Briggs and Stratton 206 Starters Guide

Transcription

1 Briggs and Stratton 206 Starters Guide

2 Engine Class Regulations The 206 engine platform was designed and engineered exclusively for racing. Each engine is hand-built in Milwaukee, Wisconsin using dedicated tooling and dies to provide a level of consistency unmatched in the industry today. The 206 is intended to simplify racing, from hitting the track to the tech process needed to ensure a level playing field at the end of the day. In combination with Briggs & Stratton Racing s slide restriction system a complete racing ladder can be developed by simply changing a carburetor slide and/or by a slide and ignition change. With the base engine the basis for today s box stock classifications, the 206 engine gives racer s and tracks the ability to have one engine, from start to finish. All Briggs & Stratton (B&S) racing engines are manufactured solely for sanctioned racing only. B&S does not recommend the products referenced herein to be used for an application outside of sanctioned racing as serious injury or death could result. This rule package has been prepared by Briggs & Stratton Racing and is intended to establish the basis for the technical control of the classes in which the 206 and 206 contact your sanctioning body.

3 This rule package covers all engine related technical specifications. For all other regulations beyond the engine please refer or contact your sanctioning body. CONTENTS 1. Briggs & Stratton Racing Class Structure These Regulations Are the Only Regulations Briggs & Stratton 206 Product Availability General Rules Things That Are NOT Permitted Engine Sealing Technical Inspection Tools Engine Ignition Switch Engine Air Filter Engine Fuel Engine Oil Oil Breather Oil Catch Container Carburetor Overflow Fuel Pump Cooling Shrouds, Covers and Blower Housings Use of Helicoils Carburetor & Intake Manifold Cylinder Head Head Gasket Ports Valves Valve Springs Rocker Arms, Rocker Ball and Rocker Arm Studs Push Rods Engine Block Valve Lift Camshaft Profile Limits Flywheel Ignition System and Ignition Timing Crankcase Clutch Starter Exhaust Header Exhaust Silencer Exhaust Protection Torque Specification Guideline Technical Inspection Tools IMPORTANT ONLINE SUPPORT RESOURCES

4 1. Briggs & Stratton Racing Class Structure The following class structure chart is intended as a reference only. Sanctioning bodies and organizations can alter the class structures to suit their driver licensing protocols. Briggs & Stratton Racing Class Structure Class Age Weight Technical Engine Package (Pounds) Configuration Kids Kart.350 Restrictor Per sanctioning body/club regulations Junior 206 with carb lock RLV pipe (#5507) Slide (#555728) 4,100 RPM Rev Limiter Novice.450 Restrictor Per sanctioning body/club regulations 206 with carb lock RLV pipe (#5506 or 5507) Purple slide (#555735) Cadet Per sanctioning body/club regulations 206 with carb lock RLV pipe (#5506 or 5507) Red Slide (#555733) Junior 1 CLUB-.490 Per sanctioning body/club regulations 206 with carb lock RLV pipe (#5506 or 5507) GREEN Slide (#555740) Junior 2 LEGACY.520 Per sanctioning body/club regulations 206 with carb lock RLV pipe (#5506 or 5507) Blue Slide (555734) ASN Nat. Junior Per sanctioning body/club regulations 206 with carb lock RLV pipe (#5506 or 5507) Yellow Slide (#555741) Briggs & Stratton 206 Senior Per sanctioning body/club regulations 206 RLV pipe (#5506 or 5507) Stock Slide (#555590) Masters Per sanctioning body/club regulations 206 RLV pipe (#5506 or 5507) Stock Slide (#555590) Cadet, Novice, Junior 1, Junior 2 and National Junior classifications require the installation of the locking cap Part # on the carburetor slide cover. It is not permitted to run the classes without the specified slide and locking cap. The locking cap must be tightened. A seal can be utilized at the discretion of the organizer, or alternatively painted by the technical officials.. 3

5 Optimization of the slide opening in Briggs & Stratton Cadet, Novice, Junior 1, Junior 2 and National Junior classes is permitted. The only allowable method of slide optimization is by removing material from the throttle cap area highlighted in RED. The use of multiple gaskets and/or machining of the slide is prohibited. Slide opening must not exceed the appropriate no go specification as per class regulations. For information on slide optimization see video section at CAUTION The risk of pushing the limit on the slide opening is an unnecessary DQ. For every.010 of slide opening, due to the efficiency limitations of this engine, is less than.1 hp. Give yourself a buffer because it makes no measurable performance differences. 2. These Regulations Are the Only Regulations a. Only the B&S Racing Department in Milwaukee can make changes to the technical specifications herein. b. B&S dealers and their agents are not authorized to alter, verbally or otherwise, any technical specifications or competition rule herein. c. Should any B&S literature, catalogues, manuals, videos, etc. be different than these regulations, these regulations take precedence. d. Changes, corrections, addendums, etc. will be submitted to sanctioning bodies and posted at for republication and will become effective on a date specified. 3. Briggs & Stratton 206 Product Availability The 206 engine products and service parts are available only through the authorized Briggs & Stratton Racing dealers. A list of authorized dealers can be found at 4. General Rules a. The terms stock, original equipment, OEM, unaltered, etc., refer to Original Equipment supplied by Briggs & Stratton. b. Only the original equipment Briggs & Stratton 206 # or Junior 206 # engines are allowed in the classes recommended herein. c. All parts must be unaltered Briggs & Stratton 206 parts specifically made for this engine by Briggs & Stratton. No aftermarket parts to be used unless specified in these regulations. d. All parts are subject to comparison with a known stock part. This includes specified and mandated aftermarket parts. Example: RLV exhaust and Silencer. e. For ALL other regulations, general safety, etc., contact your sanctioning body. Example: Chain guards. 4

6 f. The tech official, at their sole discretion, may at any time replace a competitor s sealed engine, carburetor, or head assembly with another sealed engine or known stock part. Failure to comply is grounds for disqualification. g. Briggs & Stratton 206 classes must have a serialized block. Exception: For early built engines without a block serial number the engine identification sticker must be in place and legible. If the sticker is illegible or missing the engine must be tagged with a suitable sticker or seal approved by the technical inspector. h. Standard organizational protest procedures can allow for short block inspection (seal removal) if a new, replacement short block, p/n is offered in replacement. Competitor short block to be forfeited to the series or club as terms of this procedure. 5. Things That Are NOT Permitted a. Tampering of the factory installed engine seals (2). b. Addition or subtraction of material in any form or matter. a. Exception Valve maintenance (valve job). Valve seats must remain with the factory specification of 30 and 45 degree angles only. Valve seats of additional angles and/or angles not comparable to the factory stock of 30 and 45 degrees are not permitted. Grinding of valve stem or excessive material removal prohibited. b. Exception Optimization of the slide opening in Briggs & Stratton Cadet, Novice, Junior 1, Junior 2 and ASN National Junior classes classes are permitted per section 1 guidelines. c. Blueprinting unless stated herein. d. Modification to or the machining of any parts in order to bring them to stated minimum/maximum specification, (or for any reason). e. Machining or alteration of any kind to the engine or replacement parts unless specifically stated herein. f. Deburring, machining, honing, grinding, polishing, sanding, media blasting, etc. g. Sandblasting or glass-beading any interior engine surfaces. h. No device may be used that will impede, or appear to impede, airflow to the engine cooling system. 5

7 6. Engine Sealing There are two custom, Homeland Security Tier III rated seals installed at the factory. Tampering of the seals is not permitted. Should the seals be tampered with, the engine is no longer eligible for competition. Should an engine require dismantling for any reason that requires breaking of the seals, contact Briggs & Stratton at: Briggs & Stratton Racing Seals can have either a black anodized or bare aluminum finish on both main body ends as shown. PLEASE NOTE THAT, STARTING IN 2015, A PROPRIETARY CABLE CONTAINING A BLACK STRAND WILL BE IMPLIMENTED. 7. Technical Inspection Tools Briggs & Stratton have made available a number of tools for the convenience of technical checking of components when necessary. They are indicated throughout the rule thusly: Tech Tool #. See Section 38 for tool description. The tools are available from: Sox Racing 2223 Platt Springs Rd. West Columbia, SC (803) Engine Ignition Switch The B&S ignition switch and wires must remain in stock location. It is not permitted to alter the OEM wiring. 9. Engine Air Filter The only air filter permitted is the Briggs & Stratton Green Air Filter Part # No modification to the filter element is permitted. A protective shield may be attached for wet-weather competition. It is not permitted for the protective shield to create any ram-air effect. 10. Engine Fuel Premium Gasoline no greater than 94 octane sold at normal roadside fuel stations open to the public. The addition of fuel additives in any manner is not permitted. Fuel dispensing location may be specified in Event Supplementary Regulations. 6

8 11. Engine Oil High-quality synthetic oil within a 10W-20 range recommended. No oil additives are permitted. Factory Recommendation- Briggs & Stratton 4T Synthetic Racing Oil is engineered exclusively for the rigors of high revving, air-cooled racing engines (available through both Briggs Racing and Amsoil dealers). The use of karting or automotive oils is not recommended as many are hydroscopic in nature, offer limited protection over time, and/or were engineered for pressure, not splash lube systems. The use of these oils can induce engine failure and/or accelerate wear. 12. Oil Breather Oil breather must vent to a catch container. 13. Oil Catch Container An oil overflow catch system is mandatory. Overflow tube must run from the crankcase breather to a catch container. The catch-container must be vented to atmosphere. 14. Carburetor Overflow Carburetor overflow must be vented to a catch container. 15. Fuel Pump Only fuel pump, B&S part number , is legal for competition. This fuel pump can be identified by the Briggs & Stratton diamond logo on the pump face. All other pumps are prohibited. It is prohibited to pulse from the intake manifold. Relocation of the fuel pump is legal as long as it is spaced to less than 3/4 inch off of the control plate, B&S #555699, in a similar location that is both safe and secure. Measurement is from the base of the control plate to the bottom of the fuel pump. Vertical mounting or mounting the fuel pump upside down is NOT allowed. The fuel pump must be pulsed from a pulse fitting mounted on the oil fill fitting located on the engine side cover. Aftermarket one-piece filler/pulse fittings such as shown on the right are permitted. The use of silicone sealant on the brass vent is permitted. A fuel pump return line to the fuel tank is prohibited. A fuel filter is to insure that dirt and contamination within your fuel system does not impact your carburetors performance. This is not a tech item. 16. Cooling Shrouds, Covers and Blower Housings All pieces of the engine cooling shroud/blower housing and control panel must be stock B&S and properly installed. Engine Shroud may be painted any color. Any bolt, with the exception of the head bolt, that is used to secure sheet metal shrouds and covers may be replaced with larger diameter bolts. No taping or covering of the rewind shroud is permitted. 7

9 17. Use of Helicoils It is permitted to use Helicoil thread inserts for shrouds, valve cover, oil drain, oil fill holes, blower housing, and exhaust pipe attachment studs on the head and lower brackets. 18. Carburetor & Intake Manifold The B&S stock carburetor part # is the only carburetor permitted. Walbro, Briggs diamond logo and/or # etched in the body are additional visual indicators. No alterations allowed unless stated below. All parts will be compared to a stock known B&S part for eligibility. This includes the nozzle, emulsion tube, jets, float, float needle and all other carb parts. It will be allowed however to adjust the float height by means of bending the small tab on the float arm. Slide must remain B&S stock unaltered. Slide cutaway to be measured on flat surface..075 no go Tech Tool A10. B&S stock unaltered aluminum needle is required part number marked #BGB. Needle to be inspected using Tech Tool A4. Needle, when placed in tool A4, should not protrude through the other side. If needle protrudes through the block it is out of specification. 8

10 NOTE: Slide openings should be measured only with the Briggs & Stratton slide tool listed on the tool reference chart. Class Max. Slide Height.350 Kid Kart.310 Opening (Long BLACK).450 Novice.342 Opening (PURPLE).440 Cadet.440 Opening (RED) Junior 1Club.490 Opening (GREEN) Junior 2 LEGACY.520 Opening (BLUE) ASN Nat. Junior.570 Opening (YELLOW) Technical Item Description Tech Tool a. Needle Jet C-clip Needle Jet C-clip must be properly installed but may be installed at any of the 5 factory settings on the needle jet. b. Throttle cable cap Throttle cable cap on the top of the carburetor must be used and properly installed in tight position. c. Choke Choke: OEM unaltered, but lever may be fastened open with a spring, rubber band, wire, etc. d. Idle pilot jet Idle pilot jet #32, hole size is.0130 no go. e. Main jet Main jet #95, hole size is go, no go f. Main nozzle and Emulsion tube Main nozzle OEM stock unaltered hole size =.101 min and.104 max inches. No drilling, reaming, slotting or oblonging of hole. Emulsion tube OEM stock unaltered 4 small holes =.018 min inches to.021 max inches 4 big holes =.026 min inches to.029 max inches. g. Venturi Measurement Venturi Measurement: Vertical:.792 max inches. Horizontal:.615 max inches at widest part Horizontal:.602 max inches at narrowest part. h. Air pick off hole Air pick off hole go.061 no go i. Throttle bore Throttle bore Must be as cast and bore max diameter =.874 inches. j. Venturi idle fuel hole Venturi idle fuel hole =.038 inches max k. Air filter Air filter: Only GREEN air filter, part # is allowed. Filter adapters are not allowed, filter must attach directly to carburetor air horn l. Carburetor overflow Carburetor overflow: Must be vented to a catch container. m. O-Ring O-Ring part number B&S part # is required and must be unaltered. n. Intake Intake manifold max length = inches min to manifold inches max Intake manifold bore diameter =.885 inches min to.905 inches max A8 A8 A20 o. Choke Bore A7 p. Carb Slide Cutaway.075 no go A10 q. Widest part of Combustion Chamber A30 A9 A7 A12 A11 9

11 19. Cylinder Head a. The ONLY head casting for the B&S 206 herein is the RT-1, cast into the head just off the head gasket surface (towards the rear of the engine, PTO side). The overall head minimum thickness is b. Cylinder head must be as cast. Factory machining marks left on the head gasket surface are a tech item. c. Hard Carbon may be scraped from head before measuring. d. Depth of shallow area of combustion chamber must be.030 inch minimum. This measurement to be taken with a depth gage on both the combustion side and spark plug side of cylinder head. e. Depth at floor of combustion chamber is.340 inch minimum. f. Inspect retainers for alterations that would increase valve spring pressure to.075 maximum flange thickness. Both intake and exhaust must have OE stock B&S valve keepers. g. Unaltered B&S part # (exhaust) and # (intake) can be checked for appearance, weight, and dimensions. No machining, polishing, easing, or alterations of any kind allowed. Valve surface must remain as factory, with one single 45 degree face. No other additional angles allowed on any part of the valve. Tech Tool A22. h. Valve Guides: Replacement of valve guides with B&S part # only is allowed. Maximum depth from the head gasket surface to the intake valve guide is Head Gasket a. Unaltered B&S part # is the only head gasket allowed. b. Minimum thickness allowed is.049". Measurement must be performed using a micrometer. Readings are taken from inside the cylinder hole of the gasket closest to the combustion chamber (see diagram). Four measurements must be taken with 3 meeting the minimum thickness of Ports a. No de-burring, machining, honing, grinding, polishing, sanding, media blasting, etc. b. The transition from intake bowl to port must have factory defined machining burr at this junction. No addition or subtraction of material in any form or matter. No alterations of any kind may be made to the intake or exhaust ports. c. Intake Port: Maximum diameter measurement =.918 inches max. Tech Tool A6. d. Exhaust Port AS CAST. Exhaust Outlet Tech Tool A6. e. Valve Seats. Intake and exhaust: Must remain factory specification with one 30 and one 45 degree angle only. Valve seats of additional angles and/or angles not comparable to the factory stock are not permitted. 10

12 f. Valve maintenance permitted (valve job). Valve seats must remain with the factory specification of 30 and 45 degree angles only. Valve seats of additional angles and/or excessive material removed when compared to the factory stock is prohibited. g. Intake valve seat diameter inside = maximum.972 inches. Tech Tool A2. h. Intake port pocket bowl (area just below valve seat) =.952 no go Tech Tool A2 i. Exhaust valve seat diameter inside = maximum.850 inches. Tech Tool A Valves a. Intake valve Minimum Weight of Valve Diameter of valve stem Diameter of valve head Diameter of valve seat Valve length Height from angle of valve face to top of the valve b. Exhaust valve Minimum Weight of Valve Diameter of valve stem Diameter of valve head Diameter of valve seat Valve length Height from angle of valve face to top of the valve 27.8 grams.246 to.247 inches to inches Tech Tool A inches ID maximum Minimum inches.057 inches minimum Tech Tool A grams.246 to.247 inches.935 to.945 inches Tech Tool A inches ID maximum Minimum inches.060 inches minimum Tech Tool A Valve Springs (updated 2/2/16) a. Valve Springs are single coil stock, unaltered B&S part # Must be identical in appearance to factory part and have 4.00 to 4.75 coils in stack. b. Spring Wire Diameter:.103 to.107 inches c. Valve spring length:.940 max inches Tech Tool A15 d. Inside diameter:.615 to.635 inches 24. Rocker Arms, Rocker Ball and Rocker Arm Studs a. Rocker arms must be unaltered stock B&S part # (US) or # (metric) and will not be altered in any way. b. Rocker studs must be stock, unaltered stock B&S part # (US) or # (metric) and in stock location 11

13 c. Rocker Ball must B&S stock. Diameter.590 inch min. to.610 inch maximum. Tech Tool A16. d. Rocker arm mounting positions may not be altered in any manner. No helicoiling of mounting holes. No bending of studs. e. Rocker arm stud plate must be bolted to the head with one, OEM stock B&S gasket only - no alterations. Maximum thickness of gasket is.060 inches. f. Rocker arm overall length inch minimum. Can be checked with a pair of dial calipers. 25. Push Rods a. Push rods must be unaltered stock B&S part # b. Push rod length minimum inches to maximum inches. Tech Tool A5. c. Push rod diameter.185 minimum inches to.190 maximum inches. 26. Engine Block a. Engine block must be unaltered as cast B&S factory machined condition. There must be no addition or subtractions of metal or any substance to the inside or outside of the cylinder block. b. Both (2) B&S engine seals must be present with both the fastener and seal in as shipped from the factory location and condition. Any defined tampering with the fasteners or damage to the wire/seal itself (example: delaminated hologram) are grounds for disqualification. Take proper care of your seals to ensure their integrity. It is recommended that you wrap your seals (using a plastic bag, etc.) to prevent exposure to harsh solvents such as carb cleaner, etc... c. Deck gasket surface finish is not a tech item. Piston pop up can be.005 inches maximum. Piston pop-up to be checked with flat bar in center of piston parallel to piston pin and then again checked 90 degrees to piston pin. Tech Tool A25. Angle milling or peak decking is not allowed. d. Carbon build-up can be removed before pop-up is measured as long as material is not removed from the piston. Exception Competitors can deburr the manufacturing part number/marks IF needed as long as: Removal does not extend beyond the defined script area. De-burring does not extend below the original piston surface area. The original part numbers and script are still clearly visible. e. Cylinder bore will not be bored oversize f. Cylinder bore will not be re-sleeved. g. Cylinder bore position is not be moved or angled in any manner. h. Cylinder bore dimension: - Briggs & Stratton stock bore is Allowance for wear is permitted up to maximum for entire length, top to bottom. i. Maximum stroke is Push piston down to take up rod play. Check stroke on BDC to TDC. Tech Tool A21. 12

14 27. Valve Lift a. Maximum valve lift is checked from the top of the valve spring retainer. Valves must be adjusted to zero clearance. b. Valve Lift: Camshaft check is taken at the valve spring retainers. With the lash set at zero, the movement of the valve spring retainers may not exceed the following: Intake and exhaust:.255 inches maximum. 28. Camshaft Profile Limits (measured at the push rod) Push gently down on dial indicator stem to ensure that there is no lash when push rods are going down. NOTE: Due to the extended life of the engine, a single point on each lobe can be off by a maximum of 2 degrees without issue, the exception being on the.006 check, both intake and exhaust. Intake lift Exhaust lift TO 51 BTDC TO 93 BBDC TO 12 BTDC TO 55 BBDC TO 4.5 ATDC TO 39 BBDC TO 21 ATDC TO 22 BBDC TO TO 5 BBDC TO 47 ATDC TO 5 ABDC TO 58 ATDC TO TO 72 ATDC TO 29 ABDC MAX LIFT MAX LIFT MIN LIFT MIN LIFT Intake lift Exhaust lift to 34 BBDC TO 72 BTDC TO TO TO 10 BBDC TO 48 BTDC TO.5 BBDC TO 38 BTDC TO 16 ABDC TO TO 33 ABDC TO 4.5 BTDC TO TO 12 ATDC TO 91 ABDC TO 55 ATDC 29. Flywheel a. No modifications are allowed to the flywheel. b. The minimum weight of the flywheel, fins and attachment bolts is 4 pounds 1 ounce. c. Stock B&S part # only. No machining, glass beading, sand blasting, painting or coating of flywheel is allowed. d. A flywheel fan, B&S part #692592, with broken fins must be replaced. e. Stock, unaltered B&S flywheel key with the B&S logo is required. Width of the key allowed is No offset keyways allowed. 13

15 30. Ignition System a. Unaltered B&S stock ignition part # is mandatory. Only GREEN ignition module allowed. Maximum RPM: 6,150. Exception Cadet Junior 206 class requires the use of unaltered B&S stock ignition part # (BLACK in color). Maximum RPM: 4,150. b. Coil or its position, other than air gap may not be altered in any way. Coil mounting bolts must be stock and cannot be altered in any way to advance or retard timing. Attachment bolts and/or bolt holes may not be altered. c. Spark plug: Only the B&S unaltered factory spark plug part number # Champion RC12YC is permitted. Spark plug must have the Champion and Briggs & Stratton logo as well as the RC12YC identification on the insulator. Sealing washer must be in place as from factory. d. Magneto air gap is non-tech (recommended clearance of.016 ) e. Ignition timing: Maximum of 30 degrees BTDC f. Spark plug connector: Only the OEM B&S part # is permitted. 31. Crankcase Novice class must run the supplied Max-Torque clutch, Part # No alteration to the clutch is allowed, except springs and clutch key are non-tech. 32. Clutch a. Novice class must run the supplied Max-Torque clutch, Part # No alteration to the clutch is allowed, except springs and clutch key are non-tech. b. Junior 1, Junior 2, Senior, and Masters Classes can run any rim centrifugal clutch with a maximum of 9 springs and 6 shoes. No alteration to clutch allowed, except springs. Clutch coolers are not allowed. c. Refer to your sanctioning body general rules for mandatory chain guard guidelines. 33. Starter Recoil starter, B&S part # , must be retained, as produced and intact. Starter maybe rotated. 34. Exhaust Header a. Header must be RLV Model 5507 or 5506 for all classes. b. Header length: a will measure /-.25 along the short side using a wide tape measure. b will measure /-.25 along the short side using a wide tape measure. c. Gasket and/or silicone are allowed to seal header to head. (One gasket maximum) d. Studs or bolts are permitted to fasten header to head. Bolts or nuts must be safety wired. 14

16 e. Helicoiling of the exhaust is allowed. f. Supplied header support brace is mandatory. The addition of a mechanical support bracket (no welding involved) is allowed provided that there are no alterations to the shape or dimensions of the exhaust configuration. g. Any modification for or use of an O2, EGT, CO2 sensor is prohibited. 35. Exhaust Silencer Silencer must be RLV B91XL (part number 4104) with round baffle holes only. Safety wiring of the silencer to header is mandatory. All three baffles must remain unaltered and hole size can be verified using a no-go pin gage of Exhaust Protection The header must be completely wrapped (360 degrees) with a non-asbestos, approved insulation material or sleeve starting approx. 3 inches from the exhaust flange but MUST extend to where the stock supplied RVL support (welded or clamped) meets the header. 37. Torque Specification Guideline DESCRIPTION WRENCH / SOCKET SIZE TORQUE Air Guard 7mm lb-in. ( Nm) Blower Housing 10mm & 3/8" lb-in. ( Nm) Carburetor (to manifold) 10mm lb-in. ( Nm) Cylinder Head Bolts 10mm lb-in. (20-27 Nm) Exhaust Brace Screws 10mm lb-in. (11-14 Nm) Exhaust Stud 10mm lb-in. (11-14 Nm) Flywheel Nut 15/16" ft-lbs. ( Nm) Flywheel Fan 10mm lb-in. (20-27 Nm) Intake (to cylinder) 5mm Allen lb-in. ( Nm) Oil Drain Plug 3/8" lb-in. (11-14 Nm) PVL Module 7mm lb-in. (2.3-4 Nm) Rocker Arm Stud 7/16" lb-in. (10-14 Nm) Rocker Arm Plate 10mm lb-in. ( Nm) Rocker Arm Set Screw 1/8" Allen lb-in. ( Nm) Spark Plug 5/8" Deep lb-in. ( Nm) Starter Gear #2 Phillips lb-in. (4-6 Nm) Top Control Plate 10mm lb-in. (8-10 Nm) Valve Cover 10mm Lower & 3/8" lb-in. (3.5-7 Nm) 38. Technical Inspection Tools Refer to separate document illustrating the Technical Inspection Tools 39. IMPORTANT online support resources Please refer to for a host of resources. Due to the sealed nature of this engine we highly recommend reading and viewing important documents and videos to insure a great racing experience. Located online: a. 206 Engine tips and guide supplement A must to print out and read BEFORE installing your engine! 15

17 b. Carburetor tuning guide Understand your carburetor to get the most out of your 206. c. Videos: a. Proper clutch installation Properly installing your clutch will prevent the possibility of crankshaft damage. b. Setting the float height A simple video highlighting a necessary technique to insure a properly tuned carburetor. c. Setting, measuring, and optimizing your junior slide restrictor. 16

18 Racing Performance Catalog & Reference Guide Model/Type: (Kids kart/supermileage) Model/Type: (Karting) Model/Type: (Karting/Snowmobiling/Jr. Drag) Version (REV. D) Model/Type: (Quarter Midget)

19 TABLE OF CONTENTS SAFETY...1 ANIMAL General Specs...3 Special Tools...3 Torque Specs...3 Racing Specifics...3 Optional Performance Parts...3 Highlighted Features...3 Cylinder Assembly Parts Explode...4 Head Assembly Parts Explode...5 Carburetor Assembly Parts Explode...6 Housing & Flywheel Parts Explode...7 Control Bracket & Gasket Sets Parts Explode Parts...8 Gear Reduction Unit Explode...9 NO COMPROMISES. At the end of the day the effort you put into racing directly determines your outcome. You wouldn t compromise on your approach to racing, so why would you with your oil? What if there was an oil engineered specifically for high-revving, air-cooled racing engines, methanol or gas fuels, that gives you the power of a lite oil yet the wear protection of a heavy oil? What if that oil also had the added benefits of wear protection and a corrosion inhibitor to safeguard your investment during, between, and after the season was over? COMPROMISES lead TO WhAT-IF S ANd AS RACERS ThAT ISN T PART OF OuR dna. NO MORE COMPROMISES. INTROduCING ThE BRIGGS & STRATTON 4T Full SYNThETIC OIl CuSTOM ENGINEEREd BY AMSOIl. MAXIMuM horsepower OuTSTANdING WEAR PROTECTION EXCluSIVE SYNThETIC FORMulATION EXhAuSTIVElY TESTEd ON ThE dyno ANd ON ThE TRACK designed FOR high REVVING, AIR-COOlEd RACING ENGINES Available through any participating Briggs & Stratton Racing Dealer or your local AMSOIL source of supply. (Part Number GBS 2960) Part Number: GBS2960

20 BEFORE OPERATING ENGINE Read entire Operating & Maintenance Instructions AND the instructions for the equipment this engine powers.* Failure to follow instructions could result in serious injury or death. WARNING The engine exhaust from this product contains chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm. THESE INSTRUCTIONS CONTAIN SAFETY INFORMATION TO Make you aware of hazards associated with engines Inform you of the risk of injury associated with those hazards, and Tell you how to avoid or reduce the risk of injury OPERATOR SAFETY SAFETY AND CONTROL SYMBOLS WARNING Briggs & Stratton Race engines are not designed for and are not to be used to power fun-karts, children s, recreational, or sports all-terrain vehicles (ATVs), motorbikes, scooters, hovercraft, airplane produces, or any other vehicle used outside of sanctioned racing. For information about competitive racing products, see For use with utility and side-by-side ATVs, please contact Briggs & Stratton Engine Application Center, Improper engine application may result in serious injury or death. Fire Fast Moving Parts Stop Oil Explosion Toxic Fumes Shock Slow Fuel NOTICE: This engine was shipped from Briggs & Stratton without oil. Before you start the engine, make sure you add oil according to the instructions in this manual. If you start the engine without oil, it will be damaged beyond repair and will not be covered under warranty. Choke On Off Fuel Shutoff Kickback Wear Eye Protection WARNING Fuel and its vapors are extremely flammable and explosive. Fire or explosion can cause severe burns or death. Hazardous Chemical Read Manual Hot Surface Frostbite The safety alert symbol is used to identify safety information about hazards that can result in personal injury. A signal word (DANGER, WARNING, or CAUTION) is used with the alert symbol to indicate the likelihood and the potential severity of injury. In addition, a hazard symbol may be used to represent the type of hazard. DANGER indicates a hazard which, if not avoided, will result in death or serious injury. WARNING indicates a hazard which, if not avoided, could result in death or serious injury. CAUTION indicates a hazard which, if not avoided, could result in minor or moderate injury. NOTICE indicates a situation that could result in damage to the product. WARNING Certain components in this product and its related accessories contain chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm. Wash hands after handling. When Adding Fuel Turn engine off and let engine cool at least 2 minutes before removing the fuel cap. Fill fuel tank outdoors or in well-ventilated area. Do not overfill fuel tank. To allow for expansion of the fuel, do not fill above the bottom of the fuel tank neck. Keep fuel away from sparks, open flames, pilot lights, heat, and other ignition sources. Check fuel lines, tank, cap, and fittings frequently for cracks or leaks. Replace if necessary. If fuel spills, wait until it evaporates before starting engine. When Starting Engine Ensure that spark plug, muffler, fuel cap and air cleaner (if equipped) are in place and secured. Do not crank engine with spark plug removed. If engine floods, set choke (if equipped) to OPEN/RUN position, move throttle (if equipped) to FAST position and crank until engine starts. When Operating Equipment Do not tip engine or equipment at angle which causes fuel to spill. Do not choke the carburetor to stop engine. Never start or run the engine with the air cleaner assembly (if equipped) or the air filter (if equipped) removed. When Changing Oil When you drain the oil from the top oil fill tube, the fuel tank must be empty or fuel can leak out and result in a fire or explosion. When Transporting Equipment Transport with fuel tank EMPTY or with fuel shut-off valve OFF. When Storing Fuel Or Equipment With Fuel In Tank Store away from furnaces, stoves, water heaters or other appliances that have pilot lights or other ignition sources because they can ignite fuel vapors. * Briggs & Stratton does not necessarily know what equipment this engine will power. For that reason, you should carefully read and understand the operating instructions for the equipment on which your engine is placed. 1

21 SAFETY WARNING Starting engine creates sparking. Sparking can ignite nearby flammable gases. Explosion and fire could result. If there is natural or LP gas leakage in area, do not start engine. Do not use pressurized starting fluids because vapors are flammable. WARNING Engines give off carbon monoxide, an odorless, colorless, poison gas. Breathing carbon monoxide can cause nausea, fainting or death. Start and run engine outdoors. Do not start or run engine in enclosed area, even if doors or windows are open. WARNING Rapid retraction of starter cord (kickback) will pull hand and arm toward engine faster than you can let go. Broken bones, fractures, bruises or sprains could result. When starting engine, pull the starter cord slowly until resistance is felt and then pull rapidly to avoid kickback. Remove all external equipment/engine loads before starting engine. Direct-coupled equipment components such as, but not limited to, blades, impellers, pulleys, sprockets, etc., must be securely attached. WARNING Running engines produce heat. Engine parts, especially muffler, become extremely hot. Severe thermal burns can occur on contact. Combustible debris, such as leaves, grass, brush, etc. can catch fire. Allow muffler, engine cylinder and fins to cool before touching. Remove accumulated debris from muffler area and cylinder area. It is a violation of California Public Resource Code, Section 4442, to use or operate the engine on any forest-covered, brush-covered, or grass-covered land unless the exhaust system is equipped with a spark arrester, as defined in Section 4442, maintained in effective working order. Other states or federal jurisdictions may have similar laws. Contact the original equipment manufacturer, retailer, or dealer to obtain a spark arrester designed for the exhaust system installed on this engine. WARNING Unintentional sparking can result in fire or electric shock. Unintentional start-up can result in entanglement, traumatic amputation, or laceration. Fire hazard Before performing adjustments or repairs: Disconnect the spark plug wire and keep it away from the spark plug. Disconnect battery at negative terminal (only engines with electric start). Use only correct tools. Do not tamper with governor spring, links or other parts to increase engine speed. Replacement parts must be of the same design and installed in the same position as the original parts. Other parts may not perform as well, may damage the unit, and may result in injury. Do not strike the flywheel with a hammer or hard object because the flywheel may later shatter during operation. When testing for spark: Use approved spark plug tester. Do not check for spark with spark plug removed. WARNING Rotating parts can contact or entangle hands, feet, hair, clothing, or accessories. Traumatic amputation or severe laceration can result. Operate equipment with guards in place. Keep hands and feet away from rotating parts. Tie up long hair and remove jewelry. Do not wear loose-fitting clothing, dangling drawstrings or items that could become caught. Each racer is solely responsible to check and maintain engine legality per the rule set they compete under. Due to the conditions inherent in racing, Briggs & Stratton does not warrant race engines or parts. 2

22 ANIMAL GENERAL SPECS Model: Type: Animal Jr LO M Series Displacement: Cu. in cc Design: Slant, 30 degree Overhead Valve Bore: / in. Stroke: 2.2 in. Compression Ratio: 8.5 to 1 Factory Timing: 29 degrees BTDC SPECIAL TOOL REQUIREMENTS General Model 12 Manual Part No Flywheel Holder Tool Part No PVL Flywheel Puller Part No RACING SPECIFICS PVL Ignition Module Gap -.010/.014 (.15/.36mm) Digital Rev Limiter: Max. 12,000 RPM - Part No Max. 6,100 RPM - Part No Max. 4,100 RPM - Part No Oil - Briggs & Stratton Racing recommends using ONLY 14 ounces of Briggs & Stratton 4T full-synthetic racing oil. Briggs & Stratton 4T was specially engineered and tested in conjunction with Briggs & Stratton to protect your investment from the rigors of racing without compromising performance or longevity. Air-cooled, splash lube oil system along with strict manufacturing tolerances and component materials require oil engineered for the task. We do NOT recommend the use of automotive oils as these products were engineered for pressure lubed systems and the lower operating temperatures. We also strongly recommend against the use of karting labeled oils as PAG based oils are extremely hydroscopic by nature (attract water), have a low solubility and TBN, and vaporize within the range of our operating temperatures. Briggs & Stratton 4T Racing oil, p/n GBS2960, is available through your local Briggs Racing or Amsoil dealer. TORQUE SPECS DESCRIPTION WRENCH/SOCKET SIZE TORQUE Air Guard 7mm lb-in. ( Nm) Blower Housing 10mm & 3/ lb-in. ( Nm) Carburetor (to manifold) 10mm lb-in. ( Nm) Connecting Rod T lb-in. (16-17 Nm) Cylinder Head Bolts 10mm lb-in. (20-27 Nm) Exhaust Brace Screws 10mm lb-in. (11-14 Nm) Exhaust Stud 10mm lb-in. (11-14 Nm) Flywheel Nut 15/ ft-lbs. ( Nm) Flywheel Fan 10mm lb-in. (20-27 Nm) Intake (to cylinder) 5mm Allen lb-in. ( Nm) Oil Drain Plug 3/ lb-in. (11-14 Nm) PVL Module 7mm lb-in. (2.3-4 Nm) Rocker Arm Stud US-7/16, metric-10mm lb-in. (10-14 Nm) Rocker Arm Plate 10mm lb-in. ( Nm) Rocker Arm Set Screw US-1/8 Allen, metric-4mm lb-in. ( Nm) Spark Plug 5/8 Deep lb-in. ( Nm) Side Cover 10mm (patched) lb-in. (24-26 Nm) 10mm (unpatched) lb-in. (18-19 Nm) Starter Gear #2 Phillips lb-in. (4-6 Nm) Top Control Plate 10mm lb-in. (8-10 Nm) Valve Cover 10mm Lower & 3/ lb-in. (3.5-7 Nm) HIGHLIGHTED FEATURES Dual Ball-Bearing, RACING Reinforced Cylinder Squeeze-Cast, T-7 Heat Treated, Racing Rod Ground Cam w/ Compression Release High-Silicon Valve Springs PVL Digital Ignition System Racing Only Intake Port Walbro Round - Slide Carburetor Interface Sealing Solutions Fire-ring head gasket (Animal/WF only) Racing Crankshaft w/ Induction-Hardened Crankpin Custom Cam Ground, Barrel-Faced Piston Chrome-Faced, Racing Ring Package Nitrited Dished Exhaust Valve Automotive 3-Piece Valve Retainer System Beefy Rocker Arm Stud Nuts Carbon Steel Crankshaft w/induction hardened crankpin OPTIONAL PERFORMANCE PARTS High - G/Force Breather Bypass System - Part No Magnetic Drain Plug - Part No Gearbox Splined Crankshaft - Part No Gearbox Complete - Part No (page 9) Electric Starter Kit - Part No Fuel Filter - Part No S 206 Stator Lighting System (snowmobile) - Part No ANIMAL ENGINES 3

23 ANIMAL cylinder assembly (Engine Model Series ) ANIMAL ENGINES Piston Assembly (Std.) Piston Assembly (.10 Over) Piston Assembly (.20 Over) Piston Assembly (.30 Over) Ring Set (Std.) Ring Set (.10 Over) Ring Set (.20 Over) Ring Set (.30 Over) High-G/Force Bypass Assembly (Optional, Also includes Rocker Cover Gasket) Cylinder Shield (Black) Cylinder Shield (Silver) Screw (Cylinder Shield - M4 x.7) Ring Set (.010 Over Compression Ring) Ring Set (.020 Over Compression Rings) Ring Set (.030 Over Compression Ring) Bushing/Seal Kit Breather Tube Ring Set (.10 Over - Contains 10 Top Rings) Ring Set (.20 Over - Contains 10 Top Rings) Ring Set (.30 Over - Contains 10 Top Rings) Flywheel Nut (M6 x 1.5-6H) s Oil Seal* (Magneto Side) * Crankcase Gasket * Hex Head 1" Screw (Connecting Rod - Animal/206) Hex Head 1 1/4 Screw (Connecting Rod - World Formula) Timing Gear Bearing s Oil Fill Cap Oil Seal (PTO Side) Crankshaft Connecting Rod Crankcase Cover Crankshaft Endplay Shim (Contains.007,.012,.018, &.025) s Oil Fill Cap Hex Washer Head Metric Screw (Crankcase Cover/Sump - M7 x 1) Piston Pin Lock Timing Key (0.370 ) Timing Key (0.491 ) Camshaft (Machined) Camshaft (Unmachined) Oil Drain Plug* Oil Drain Plug (Magnetic, Optional) Cylinder Assembly Locating Pin* Ball Bearing s Flywheel Key World Formula Billet (Optional) Connecting Rod Piston Pin *Included with Cylinder Assembly (Includes all parts shown) Included with Respective Piston Assembly (Includes all parts shown) Included with Crankshaft Repair Manual Included with Crankcase Cover

24 ANIMAL head assembly (Engine Model Series ) Hex Washer Head Screw (Rocker Cover Top & Sides) US Rocker Arm Adjuster Kit* Metric Rocker Arm Adjuster Kit** US Rocker Arm Stud* Metric Rocker Arm Stud** Hex Washer Head Metric Screw (Cylinder Head Plate - M6 x 1) Push Rod Guide* US Cylinder Head Plate* (w/ gasket) Metric Cylinder Head Plate** (w/ gasket) Cylinder Head Plate Gasket* Hex Washer Head Metric Screw (Rocker Cover Bottom - M6 x 1) Rocker Cover (Black) Rocker Cover (Silver) Low Profile Rocker Cover (unpainted, snowmobile applications) Rocker Cover Gasket US Rocker Arm* Metric Rocker Arm** (Both with Briggs & Stratton logo) Valve Retainer* Valve Spring* (Intake & Exhaust) Heat Disperser (Optional) ANIMAL ENGINES Hex Washer Head Metric Screw* (Cylinder Head - M8 x 1.25) Spark Plug (Champion RC12YC) Valve Guide Bushing* (Standard) Valve Guide Bushing (.002" Over) Cylinder Head Assembly Factory Cut Cylinder head (.011 Rule) Cylinder Head Gasket (Fire Ring) Cylinder Head Gasket (Standard - LO 206 Engines) Push Rod Intake Valve* Exhaust Valve* Valve Tappet **Included with Cylinder Head Assembly *Not interchangeable with metric rocker system parts. 5

25 ANIMAL carburetor assembly (Engine Model Series ) ANIMAL ENGINES Carburetor Locking Cap (206 Program) Throttle Cable Boot* Throttle Cable Cap Throttle Return Spring Needle Valve Retainer (Contains 5 Clips & 5 Retainers) Green Air Filter (Standard on LO 206, Optional on Other Models) Green Air Filter (Snowmobile version*) Needle Jet (BGB Gasoline) Needle Jet (DID Alcohol) Mikuni Fuel Pump Throttle Cable Cap Gasket* Choke Cover (Optional) Needle Jet (Alcohol, Needle only, BHA) Throttle Valve Extended Throttle Valve (Jr. LO 206) Choke Cover Plate Metric Screw (Carburetor Spacer to Cylinder Head - M6 x 1) Carburetor Spacer Intake Gasket* Idle Speed Kit Emulsion Tube O-Ring Seal* Idle Mixture Kit Hex Flange Metric Nut/Screw (Carburetor to Spacer - M6 x 1) Pilot Jet Main Nozzle (Walboro Part Numbers) Gas Alc TS Available through Walboro Stock 95 Main Jet (Gasoline - Contains: 30 & 34 mm Pilot Jets: 93, 95, 96, 98 & 100mm Main Jets) Main Jet (Alcohol - Contains: 1 Alcohol Main Nozzle; 38, 40 & 42mm Pilot Jets: 135, 137, & 140mm Main Jets & 1 Alcohol Needle) Main Jet (Blank Contains: 5 pcs) Stock Main Jet Needle Float Valve Hex Washer Head Metric Screw/Nut (Carburetor to Spacer - M6 x 1) Carburetor Float Pulse fitting (coming in February 15) Not avaliable through Briggs & Stratton Walboro Part Number (M4 x.07 x 12) Float Bowl Gasket Float Bowl Only available in Float bowl assembly * Carburetor Overhaul Kit Curved Intake (coming in February 15) O-Ring Seal* Carburetor Bowl Drain (Used after Code Date ) Carburetor Bowl Drain (Used before Code Date ) Carburetor Assembly (Does not contain Spacer, Gasket, Mounting Screws or Main Jets) 6

26 ANIMAL housing & flywheel (Engine Model Series ) Stator Lighting System ANIMAL ENGINES (optional) Magneto Armature (Animal - 12,000 rpm) Magneto Armature (206-6,100 rpm) Flywheel & Ignition Kit (includes (fan) and x 2 screws) Magneto Armature *Flywheel only available in kit Regulator Stator Stator Screw (1 pc, 4 needed) (Jr ,100 rpm) Flywheel PVL Magneto Wire (includes (fan) and x 2 screws) Metric Screw (Magneto Armature - M4 x.7) Stop Wire (Used on Type No & 8003) Screw (Flywheel Fan - M8 x 1.25) Starter Gear (Includes 4 Pcs Screw, Optional for Electric Start) Blower Housing Flywheel Fan Hex Washer Head Metric Screw (Blower housing M6 x 1) Flywheel Washer Hex Jam Nut (Flywheel - M16 x 1.5-6H) Flywheel Guard Metric Screw (M5 x.8) Hex Washer Head Screw (M4.2 x 1.4) Hex Washer Head Screw (Blower Housing - 5/16-18unc) Rewind Guard Flywheel Puller Flywheel Wrench Flywheel Cup (Optional) Rewind Starter (Optional) (Contains 4 pcs - M5 x.8) Starter Kit Electric Start Conversion Kit Includes Starter Assembly Starter bracket Starter Gear Starter Drive Cover 7

27 ANIMAL control bracket & gasket sets (Engine Model Series ) ANIMAL ENGINES 206 PARTS MetricScrew (Control Panel - M6 x 1) Control Panel *Included with Engine Gasket Set Crankcase Gasket* s Oil Seal* (Magneto Side) Sealed Shortblock Oil Seal* (PTO Side) Carburetor Locking Cap Starting Switch + Included with Valve Gasket Set Intake Gasket* Cylinder Head Plate Gasket* Junior Throttle Slide Junior Throttle Slide Cylinder Head Gasket*+ (Fire Ring) Max-Torque Clutch, 3/4 crank, 17 tooth, 35 chain Junior 206 Throttle slide Black Junior 206 Throttle slide Black Club Throttle slide Red Club Throttle slide Blue CA Novice Throttle slide.342 Purple CA Junior Club Throttle slide Green CA Junior National Throttle slide.570 Yellow Green Air Filter Stop Wire (Used on Type No. 8003) Stop Wire (Rocker Switch, Used on Type No & 8002) Rocker Cover Gasket* Ignition Module, 6,100 rpm limiter Junior PVL Ignition Module, 4,100 rpm limiter 8

28 ANIMAL gear reduction unit (Engine Model Series ) Ball Bearing Timing Gear Gear Case Gasket Crankshaft S Oil Seal Complete Gearbox (minus crankshaft) Splined Racing Crankshaft Gear Reduction Case (Includes S Oil Seal) O-Ring Oil Level Vented Hole Plug (3) Oil Fill Hole Plug Sealing Washer 11 mm Hex Head Cap Screw (4) (Gear Reduction Cover - M8 x 1.25) ANIMAL ENGINES Ball Bearing 12 mm Hex Head Cap Screw (4) (Gear Reduction Case - 5/16-24) 1/2" Auxiliary Drive Shaft (Internal Gear) 11 mm Gear Reduction Cover Steel Gear Hub The use of aluminum gear hubs will result in sungear keyway damage due to insufficient keyway surface area to transfer load and a material weakness that causes the hub to twist under force Rubberized Sealing Washer Ball Bearing Gear Reduction Seal Oil Drain Hole Plug 8 mm Vented Oil Fill Plug Position Important: The vented oil fill plug in the cover must mount in the 12 o clock position. IMPORTANT Engine seal must be removed before installing this gearbox. 9

29 BRIGGSRACING.com facebook.com/briggsracing For support videos, engine carburetor setup and general guides please visit Stop by and take advantage of our racing forums to ask others questions and advice as well! Due to the conditions inherent in racing, Briggs & Stratton does not warrant race engines or parts. MS5701 (REV. D) BRIGGS&STRATTON CORPORATION POST OFFICE BOX 702 MILWAUKEE, WI USA Briggs & Stratton Corporation

30 206 RACING CLASS STRUCTURE AND SLIDE INFORMATION Briggs & Stratton Racing Class Structure Class Age Weight (Pounds) Engine Package Technical Configuration Cadet.310 Restrictor Junior 206 with carb lock RLV pipe (#5507) Slide (#555728) 4,100 RPM Rev Limiter Novice.342 Restrictor 206 with carb lock RLV pipe (#5506 or 5507) Purple slide (#555735) Junior 1 LEGACY Club with carb lock RLV pipe (#5506 or 5507) Red Slide (#555733) Junior 1 CLUB Per sanctioning body/ 206 with carb lock RLV pipe (#5506 or 5507) Green Slide (#555740) Junior 2 LEGACY.520 club regulations 206 with carb lock RLV pipe (#5506 or 5507) Blue Slide (555734) ASN Nat. Junior with carb lock RLV pipe (#5506 or 5507) Yellow Slide (#555741) Briggs & Stratton 206 Senior 206 RLV pipe (#5506 or 5507) Stock Slide (#555590) Masters 206 RLV pipe (#5506 or 5507) Stock Slide (#555590) Class.350 Cadet.450 Novice Junior 1 Briggs & Stratton 206 Junior Slide Height Openings.310 Opening.342 Opening.440 Opening.520 Opening Racer Measurement Tool 7.8 mm drill blank (.307) R drill blank (.339) 7/16 th drill blank (.437) 33/64 th drill blank (.516) Engine Speed (rpm) PURPLE SLIDE.342 Opening Corr. Corr. Torque HP (ft-lbs) (hp) Purple Slide Engine Speed (rpm) BLUE SLIDE.520 Opening Corr. Corr. Torque HP (ft-lbs) (hp) Blue Slide Engine Speed (rpm) RED SLIDE.440 Opening Corr. Corr. Torque HP (ft-lbs) (hp) Red Slide Engine Speed (rpm) YELLOW SLIDE.570 Opening Corr. Corr. Torque HP (ft-lbs) (hp) Yellow Slide Engine Speed (rpm) GREEN SLIDE.490 Opening Corr. Corr. Torque HP (ft-lbs) (hp) Green Slide Engine Speed (rpm) STOCK, UNRESTRICED 206 Corr. Corr. Torque HP (ft-lbs) (hp) Stock Slide These net power curves are to be used as a guide for initial gearing and clutch recommendations. Net performance values have been obtained and corrected in accordance with SAE J1349 Engine Power Test Code - Net Power Rating. Net power values are taken with exhaust and air cleaner installed. These have been obtained from test results of a limited number of engines and have not been proven to be statistically significant. Given the wide array of factors which can affect engine performance such as, but not limited to, final engine trim (air cleaner, exhaust, sanctioning body rule variances), equipment set-up, application limitations, ambient operating conditions (temperature, humidity, altitude), etc. These curves are intended as a reference for gearing and clutch setup only.

31 Briggs & Stratton Racing Carburetor Tips and Reference Guide Animal, 206, and M-series PZ-22 World Formula PZ-26 Version (REV. -)

32 PZ CARBURETOR PERFORMANCE TUNING AND MAINTENANCE All information provided is intended for use as a guideline for basic operation, tuning, and maintenance of the PZ slide valve carburetor used on your Briggs & Stratton race engine. Contents: TUNING 1 Idle and Low Speed 2 Midrange/Part Throttle 3 High Speed/Full Throttle 3 TUNING TIPS 4 SET-UP 4 MAINTENANCE 5 SPECIFICATIONS & EXPLODED VIEWS 5 SAFETY NO COMPROMISES. At the end of the day the effort you put into racing directly determines your outcome. You wouldn t compromise on your approach to racing, so why would you with your oil? What if there was an oil engineered specifically for high-revving, air-cooled racing engines, methanol or gas fuels, that gives you the power of a lite oil yet the wear protection of a heavy oil? What if that oil also had the added benefits of wear protection and a corrosion inhibitor to safeguard your investment during, between, and after the season was over? COMPROMISES lead TO WhAT-IF S ANd AS RACERS ThAT ISN T PART OF OuR dna. NO MORE COMPROMISES. INTROduCING ThE BRIGGS & STRATTON 4T Full SYNThETIC OIl CuSTOM ENGINEEREd BY AMSOIl. MAXIMuM horsepower OuTSTANdING WEAR PROTECTION EXCluSIVE SYNThETIC FORMulATION EXhAuSTIVElY TESTEd ON ThE dyno ANd ON ThE TRACK designed FOR high REVVING, AIR-COOlEd RACING ENGINES Briggs & Stratton 4T Racing Oil is available through any authorized Briggs & Stratton Racing dealer. For additional information or to locate a dealer near you please visit As with any carburetor or fuel system, care must be taken to avoid fire from leaking or spilled fuel. Be sure all gaskets and seals are in good condition and properly assembled. Dispose of any drained or spilled fuel. Check condition of fuel lines and connections before every use. Fuel must be drained from the system if vehicle or engine is not stored or transported in a level position. It is necessary to check the carburetor slide for free movement through the full range of travel any time the carburetor has been removed, installed, or adjusted and before starting the engine. Remove air filter and visually confirm the slide valve is fully closed as the throttle is released. Work the throttle control from closed to fully open and watch for any sticking or hang-up. Engines could start with an open throttle resulting in a runaway vehicle. Always install the correct return spring for the carburetor and use an additional return spring on the throttle pedal as needed. Motorsports are dangerous and can lead to injury or death. Part Number: GBS2960

33 TUNING Rich and Lean: An internal combustion engine needs a specific ratio or mixture of air and fuel for best performance. This mixture is delivered by the carburetor. In the following discussion numerous references will be made to the air and fuel mixture (air/fuel ratio) being rich or lean. Rich refers to a mixture with an excess of fuel. Lean refers to a mixture with an excess of air. Float height Parts involved: Float Inlet Needle The float height controls the fuel level in the float bowl. This adjustment determines the point at which the inlet needle opens as the fuel level drops in the bowl. Float height is usually measured with the float bowl removed and is specified from the carburetor body to an edge or surface on the float. The float should be resting on the inlet needle but not depressing the spring under the needle stem when this measurement is taken. To adjust, carefully bend the tab where it makes contact with the inlet needle. The float height should be adjusted before any other adjustments are made. A higher fuel level will cause a richer mixture and possibly excess overflow from the vents. A lower fuel level will a cause a leaner mixture and could lead to an engine miss or cut-out while cornering. Start at the specified height and change as needed for best performance on different type of tracks. The float drop should also be checked. The proper adjustment will prevent the needle from pulling too far out of the inlet seat and becoming stuck in the open position. Animal, 206, and M-series World Formula 1

34 Idle and Low Speed Parts involved: Idle Speed Screw Idle Mixture Screw Pilot Jet (Idle Jet, Slow Jet) Carburetor tuning at idle and low speed is accomplished by adjusting the Idle Mixture Screw, the Pilot (or Idle) Jet, and Idle Speed Screw. These adjustments will control idle speed, idle quality, and initial responsiveness/ acceleration of the engine. The screw in the center of the side of the carburetor body is the Idle Speed adjustment. This screw holds the throttle slide valve open slightly to obtain the desired engine rpm at closed throttle. Turning the idle speed screw clockwise will increase rpm. Turning counter-clockwise will decrease rpm. The Pilot Jet is screwed into the carburetor body and is located inside the float bowl. (See photo, next page.) The Pilot Jet meters the amount of fuel entering the low speed circuit. A larger or smaller jet will change fuel flow accordingly. The size of the jet in millimeters is stamped on it. mixture screw will usually result in the highest rpm with the throttle closed. As the amount of fuel is varied the engine rpm will also vary. With throttle closed and engine warm and running at or slightly above desired idle speed, slowly turn the Idle Mixture Screw in or out to obtain the highest rpm. Then set the idle speed screw to obtain the desired rpm. If a smooth idle cannot be set with the idle mixture screw between ¼ to 2-¼ turns out, or if the engine does not respond to adjustment, a different size Pilot Jet may be needed. The pilot jet, also called idle or slow jet, controls the amount of fuel at idle and throttle positions up to ¼ open. If the mixture needle cannot be leaned out enough, a smaller Pilot Jet should be installed. A larger jet should be installed if the mixture is too lean. The proper Pilot Jet size will allow a satisfactory setting with the mixture screw. World Formula Animal, 206, and M-series The Idle Mixture Screw can be either an air or fuel adjustment so it should be determined what type of change you are making. A mixture screw on the air filter side of the PZ22 carburetor is an air-only adjustment so opening the screw (turning counterclockwise) will increase the air bleed and lean the mixture. The mixture screw on the engine side of the PZ26 carburetor is a fuel adjustment. Opening the screw will allow more fuel into the engine for a richer mixture. For an initial setting, gently turn the mixture screw in until it lightly seats or stops. Back out the specified number of turns. The optimum setting of the 2

35 Midrange/Part Throttle Part involved: Jet Needle Main Nozzle (Needle Jet) Throttle Slide Valve The Jet Needle primarily controls fuel flow between 10% and 75% throttle opening. The Jet Needle is the long narrow needle in the center of the throttle slide valve. The needle can be seen when the throttle is opened. It is held in place in the center of the throttle slide by a V-shaped clip. The Jet Needle has five notches and a C-clip which determines the position of the needle in the slide based on which notch the clip is placed in. By varying the height of the needle in relation to throttle opening, the amount of taper of the needle in the main nozzle will change the fuel mixture. To richen the part throttle operation, move the clip to the next lower notch. This will hold the needle farther out of the main nozzle and allow more fuel into the air stream. To lean part throttle operation move the clip to the next higher position. The notch at the top of the needle would be considered the first position (leanest). Needle taper reference letters are stamped on the needle for identification. Location of C-clip on jet needle determines midrange fuel mixture. RAISING THE NEEDLE IN THE SLIDE = RICHER MIXTURE LOWERING THE NEEDLE IN THE SLIDE = LEANER MIXTURE Be sure the V-shaped jet needle retaining clip is in place and will hold the jet needle securely in the slide. High Speed/Full Throttle Parts Involved: Main Jet The Main Jet controls the fuel flow at throttle positions of one-half to full throttle. The Main Jet is located inside the float bowl and is screwed into the bottom of the Emulsion Tube in the center of the carburetor body. The jet size or diameter in millimeters is stamped on the jet. A larger diameter jet allows more fuel flow and a richer mixture. Altitude and weather conditions can affect the engine operation enough to require changing the size of the Main Jet. High air temperature, humidity, or altitude could require a smaller Main Jet. Low temperature, humidity, or altitude would require a larger diameter Main Jet. Animal, 206, and M-series World Formula RUNNING THE ENGINE WITH AN IMPROPER MAIN JET COULD RESULT IN A LOSS OF POWER, HIGH ENGINE TEMPERATURES, OR ENGINE DAMAGE. 3

36 TUNING TIPS Gasoline is the typical fuel used for internal combustion engines. In some racing applications methanol alcohol is used for fuel. When using alcohol the engine must consume approximately twice as much fuel as with gasoline. For this reason some parts need to be replaced for proper tuning. The main nozzle, main and pilot jets, and the jet needle need to be replaced with the proper size. If a carburetor has been working well and then develops a problem, the most likely cause is dirt or contamination in the carburetor. Dirt can plug jets or get stuck in the inlet needle and cause flooding. It will save time in the long run to be sure you are working with a clean carburetor. If the engine performance seems to change or idle/low speed running seems erratic, check for loose carburetor and manifold mounting bolts or leaking gaskets or seals. This can cause a vacuum leak and lean condition. Symptoms of a rich mixture are: Black smoke or popping in the exhaust A flat running engine or dull sound Runs worse as engine warms Symptoms of a lean mixture are: High cylinder head or exhaust temperature Backfire/popping from the carburetor Runs better with partial choke Surging or cutting out Pinging or rattling sound from engine under load The Pilot Jet, Idle Mixture Screw and Jet Needle will have the most effect on acceleration from closed throttle. A slightly rich idle mixture may help acceleration. Moving the position of the Jet Needle clip is a good quick adjustment for a change in air temp. This will help with throttle response and corner exit. The Main Jet will have the greatest effect at wide open throttle but will also affect mid-range operation. After a Main Jet change it may be necessary to move the Jet Needle position for best results. The optimum float height setting may change from track to track. A rough track or an engine misfire in certain corners may require a float adjustment. If the carburetor can be rotated on the manifold, it may help to turn the carburetor a few degrees to compensate for a problem corner or for oval tracks. 4 SET-UP The throttle/pedal ratio is an item that can be tailored to suit the driver s style and benefit overall engine performance. By changing the distance from the pedal pivot to the point the throttle cable or linkage attaches to the pedal, the carburetor action can be slowed down to help throttle control on a slick or rough track or smooth out a choppy driver. IT IS IMPORTANT TO HAVE A FIXED STOP ON THE THROTTLE PEDAL. This will reduce wear on the throttle cable and carburetor. Remove the air filter and visually confirm that the throttle slide reaches the wide open position just as the pedal hits the stop. The slide should also fully close with some slack in the cable with the pedal released. Idle speed cannot be set if the pedal is holding the slide partially open. Seal the pedal end of the cable housing from dirt. Dirt will migrate up the throttle housing especially on a dirt track. Grit or debris on the slide could cause sticking. A rubber cap can be used on the end of the cable housing with a small hole through it for the cable to slide through. A dab of silicone could also be used at the end of the cable housing. The cable housing should also be sealed by the rubber boot on the top of carburetor cap. For the cable hook-up, remove the cover, spring and slide assembly. USE CAUTION while unscrewing the cover as it will have spring tension behind it. Make a note of the orientation of the slide valve. The small groove on the side will align with a small guide pin in the bore. Thread the cable first thru the boot and cover, then thru the center of the spring and finally thru the top of the slide and hook the ball end under the bottom of the slide. (See photo.) The hose attached to the bottom of the carburetor is for fuel overflow from the bowl. It should be routed down for proper draining. Fuel pressure requirements are 1-3 psi.

37 MAINTENANCE Draining carburetor The carburetor should be purged of alcohol at the end of every day of running. Alcohol is very corrosive and will cause a lot of problems if left in the carb. The fuel line should be unhooked at the carburetor and the bowl drain screw opened to drain any fuel in the system. Another option is to run the engine on gasoline until it stalls. This will flush any alcohol out of the system. The carburetor should also be drained at least at the end of the season when running gasoline. Filters Always use an inline fuel filter to prevent contamination inside the carburetor. Air filters should fit the carburetor properly and be kept clean. Bowl gasket When reinstalling the float bowl you may find the gasket does not fit properly. If the gasket is too small it can be stretched to fit the groove. If it is wet it may swell slightly and can be set aside to dry and return to the proper size. If you are doing a lot of disassembly for tuning it may help to have extra gaskets. Cleaning/Inspection Once a year the carburetor should be disassembled for cleaning and inspection. Look for wear on the jet needle and inlet tip. Inspect and/or replace o-rings and seals. If cleaning is necessary a toothpick will work for clearing any holes such as jets. Remove the Inlet Needle and use a Q-tip to clean the inside of the inlet seat. Compressed air is also useful to remove contamination. The pilot jet has a very small metering orifice. If it cannot be blown out it will likely need to be replaced. Always use a stop on the gas pedal. This reduces wear on the carburetor and the chance of a stuck throttle. SPECIFICATIONS & EXPLODED VIEWS World Formula Main Jet: 96 Pilot Jet: 38 Main Nozzle Diameter: 2.6 Jet Needle: CDB/3rd notch Mixture Screw: 1 turn Float Height: 14mm (.550in) Animal, 206, and M-series Main Jet: 95 Pilot Jet: 32 Main Nozzle Diameter: 2.6 Jet Needle: BGB/2nd notch Mixture Screw: 1 ½ turn Float Height: 22.0mm (.860in) 5

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