Two Stroke Engines Snowmobile Engines Disassembly

Transcription

1 Name: Two Stroke Engines Snowmobile Engines Disassembly Objectives: The Student Will Be Able To: 1. Appreciate teaching methods and safety practices used in the small engine disassembly/assembly; 2. Properly disassemble all components of the two stroke engine 3. Document problems, missing or damaged pieces, take measurements, and compare to manufacture specifications, and organize and label all parts disassembled. I. Introduction: The gasoline engine consists of many parts that function together as a smooth power team. It is important to be able to identify these parts and explain how they fit and work together. Students are to disassemble a two stroke snowmobile engine, cleaning and repairing all parts, documenting the missing or broken parts, and reassembling. At the beginning of this lab the instructor will properly disassemble an engine that will be similar to yours. It is your job to pay close attention to the techniques used, as well as to take detailed notes for your own purposes. The following disassembly procedure will take you step-by-step for taking apart all the internal parts of the engine. The procedure is generic in that it works with a number of different types of engines that are present in the lab. It is important that you remember that this is not a race! Careful attention should be given to each step. Remember, there are no stupid questions! If you cannot remember how to do something, please stop and ask! Required Materials: Tool Set & Factory Manual Eye Protection Red Rags 10 Zip-Lock bags

2 II. Engine Information: Engine Make:. Model Number:. Type & Code Number:. Engine Stroke/Cycle:. Horsepower:. Vertical Shaft: Horizontal Shaft: III. Lecture Oriented Disassembly Procedure: 1. Cylinder Head Remove all the cylinder head bolts, and put them in a bag. After taking the head off, identify the following: -Head Gasket: Good Broken/Damaged Not present 2. Cylinder Measurements As you have learned before, the size of an engine is described by the size in volume when the combustion chamber is at its biggest. This occurs when the piston is at Bottom Dead Center (BDC). The volume is found by multiplying the height of the cylinder by the area of the circle. I. Turn the crankshaft s the piston is at BDC. II. Use the telescoping guage and a 2-3 micrometer to find the diameter of the cylinder. YOU MUST SHOW YOUR WORK TO RECEIVE FULL CREDIT! -Cylinder Diameter: inches -Manufacturer Specifications: inches III. Now you must find the area of the cylinder. IV. Area is calculated by the formula (π x r²) you know the diameter, so to find r, you must divide the diameter by two before putting the number into the equation. YOU MUST SHOW YOUR WORK TO RECEIVE FULL CREDIT! -Cylinder Area: inches²

3 V. Now you have to find the height of the cylinder VI. Use the digital caliper to find the full height of the cylinder, with the piston at complete bottom dead center. Height of Cylinder: inches VII. Now the volume of the cylinder is calculated VIII. Simply multiply the area by the height to get the volume in inches³. SHOW YOUR WORK! Volume of Cylinder: inches³ IX. Now we need to determine the size of the engine by multiplying the area of the cylinder by the number of cylinders in the engine. Cylinder Volume: x Number of Cylinders: = inches³ X. Small engines are usually measured in Cubic Centimeters, so we will now convert the answer from the last question to Cubic Centimeters. XI. Multiply you answer by to get Cubic Centimeters x = Centimeters³ 3. Engine Externals Remove all externals from the engine such as the: carburetor, coil, starter/recoil, exhaust, and intake. Also remove any shrouds or covers. Recoil Condition: Good Bad INSTRUCTOR CHECK BEFORE MOVING ON!!!!! SIGNATURE: 4. Clutch The clutch in these engines is a centrifugal type of clutch. It will have an outer housing that needs to be removed, the actual clutch with the centrifugal components (springs, rollers), and the inner clutch, which may need to be removed with a puller. Condition of Clutch: Missing Parts Damaged Seized Good

4 5. Cylinders The cylinders in these engines are not part of the block. They are to be removed and pulled upwards, leaving the pistons behind. 6. Crank Case The crank case on these engines usually consist of an upper and lower crank case. Split the crank case, and remove the pistons. Conditions of Crank Seals: Need Replaced Good 7. Crank Shaft Take all journal measurements of the crankshaft using a micrometer, and record them. SHOW YOUR WORK!!!! Connecting Rod Clutch Side: Connecting Rod Starter Side: Bearing Journal Outer Clutch Side : Bearing Journal Outer Starter Side: Bearing Journal Inner: Condition: Good Bad

5 INSTRUCTOR CHECK BEFORE MOVING ON!!!!! SIGNATURE: 8. Valves Snowmobile engines do not used a very complex valve system. Note the type of valve system and remove it from the block. Reed Valve Ports Rotary Valve 9. Carburetor Remove the float bowl from the carburetor, and check the condition of all the valves and needles. Some of these engines may have a diaphragm fuel pump on them. BE CAREFUL WHEN WORKING WITH THE CARBURETOR, THESE PARTS ARE SMALL AND CANNOT BE DAMAGED!!!!!!!!!!!!!!!! INSTRUCTOR CHECK ON CONDITION OF CARBURETOR --CALL ME OVER BEFORE PUTTING THE CARB BACK TOGETHER!!! SIGNATURE: