Maico Observations / Modifications - N. Moreland

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Daniel Brooks
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Maico Observations / Modifications - N. Moreland 30-11-2011 NOTE: All drawings have no tolerances included because I only created them for myself and I knew what the tolerances needed to be 1.

1 Maico Observations / Modifications - N. Moreland NOTE: All drawings have no tolerances included because I only created them for myself and I knew what the tolerances needed to be 1. A 250 clutch basket and primary drive sprocket, fitted to a 440 is not recommended. Because of the ratio differences in the primary drives, 18:41 (250cc) 21:39 (440cc), the clutch plates have to deal with an additional 22% of torque, i.e. (21 39) (18 41) = 1.22 Not only does the clutch experience 22% more torque, making it more likely to slipping, the whole gearbox experiences the extra torque also, hence you've a greater chance of breaking a gear. 2. The older clutch baskets, which were designed to run on a bronze bush, should not be run on needle rollers. The later clutch baskets have their bore hardened while the early ones are soft. Running the needle roller in the soft bore means the bore will get destroyed. Just scratching the clutch basket bore with a point of a screwdriver will let you know if it's hard or not. The soft type will scratch, the hard one won't.

clutch basket), has a bigger bore than the gear off my 440cc clutch basket. The 440cc gear bore measures Ø33.

2 3. The gear off the back of my 250cc basket, (i.e. the kickstart pinion gear which interacts with the ratchet on the rear of the clutch basket), has a bigger bore than the gear off my 440cc clutch basket. The 440cc gear bore measures Ø33.15mm, while the 250cc gear bore measures Ø33.35mm. This means that although the 440cc gear can't be fitted to the 250cc basket, it's just too small, you can fit the 250cc gear to a 440cc basket by mistake. 0.45mm 250 GEAR ON 440 BASKET 0.25mm 440 GEAR ON 440 BASKET

4. Corte Cosso shock rework. Here s what s inside. The first time I tried to open the shock it was a mystery. It probably took me an hour, but now it takes about two minutes.

Instead of trying to lever off the clip, I just pushed straight in using the Oboe nail, forcing the Oboe under the end of the clip. Once I got the Oboe in, it was straight forward, taking it apart.

3 4. Corte Cosso shock rework. Here s what s inside. The first time I tried to open the shock it was a mystery. It probably took me an hour, but now it takes about two minutes. I found the easiest way to remove the spring retaining clips, was to sharpen an Oboe nail into a really sharp point, on a bench grinder. Instead of trying to lever off the clip, I just pushed straight in using the Oboe nail, forcing the Oboe under the end of the clip. Once I got the Oboe in, it was straight forward, taking it apart. The picture below shows all the parts in the order and orientation they were disassembled. All the upwards facing faces of each shock component shown, would in reality be facing the ground when fitted to the bike. The reservoirs modified components assembly is shown best in the sectional 3D model a few pages further on.

4 CORTE COSSO SEAL HOLDER 1979 MAICO-ASSEMBLY-TO SUIT 22 X 11.5 X 4 SEAL

5 CORTE COSSO SEAL HOLDER 1979 MAICO-ASSEMBLY-TO SUIT 22 X 11.5 X 4 SEAL

6 POLYTURETHANE SEAL CIRCLIP STILL NOT FITTED

7 SECTION THROUGH MODIFIED PRESSURE VESSEL ASSEMBLY

8 Corte Cosso pressure vessel mod to include charging valve. Full travel of shock with bumper removed = 110mm. Ø11.5 rod displaced by 110mm = 11.4cc This equates to 11.2mm displacement of the Ø36mm piston shown below (Item 2) The 63mm dimension shown below was a just my best guess, based on a Corte Cosso service sheet I found for a later piggyback design.

5. I bought a re-manufactured kickstart quadrant gear, and the re-manufactured mating kickstart pinion gear. Both these parts mate together perfectly.

What this means is that they are okay to replace as a pair, but it's not a good idea to mix and match old with new.

I reckon Maico included some correction factor in their kickstart drive teeth profiles, to help overcome their poor kickstart design.

10 5. I bought a re-manufactured kickstart quadrant gear, and the re-manufactured mating kickstart pinion gear. Both these parts mate together perfectly. However, they don't have the same involute tooth profile as the original Maico parts. What this means is that they are okay to replace as a pair, but it's not a good idea to mix and match old with new. The original Maico tooth profile was more pointy, while the re-manufactured teeth just look like any conventional gear tooth profile. I reckon Maico included some correction factor in their kickstart drive teeth profiles, to help overcome their poor kickstart design. What I mean is, a pointy tooth on a gear is less likely to meet exactly with a pointy tooth on its mating gear, when the user attempts to engage the kickstart gear to start the bike. Conversely, with conventional teeth profiles, which have a small flat on top of the tooth, there is a much greater chance of locking up of the kickstart drive, when engaging the kickstart. Locking up is therefore much more likely to happen on the re-manufactured parts, due to the flat land on top of the gear teeth profiles. If you look at the photos you might wrongly assume that the only difference is wear. It's not true. Look at the roots of the teeth and you can clearly see a different tooth profile. The older teeth are narrower at the base of the valley, so obviously can't be more worn than the new gear which has a wider base to its valley. When I try to run old on new, the tip of the new tooth is digging in to the flank of the old tooth. You can actually feel it trying to dig metal out of the mating flank. It wouldn't be too long, before running old on new, that you would be creating some scrap I imagine, or at least a lot of filings. Original Maico on Maico Good Remanufactured on remanufactured Good Remanufactured on Maico Bad

6. I heard so many horror stories of scrap chains being sold, that I phoned IWIS in Germany, after Harry McQuaid told me they were the chains that Maico had fitted as standard, (http://english.iwis.

I phoned him, and he was able to give me the whole history of IWIS, saying that he sponsored Carl Pope 30 years ago on a Maico. (Sorry-that s before my time, I never heard of him).

11 6. I heard so many horror stories of scrap chains being sold, that I phoned IWIS in Germany, after Harry McQuaid told me they were the chains that Maico had fitted as standard, ( IWIS Germany put me in touch with the bloke that used to run IWIS in the UK, who has since retired. I phoned him, and he was able to give me the whole history of IWIS, saying that he sponsored Carl Pope 30 years ago on a Maico. (Sorry-that s before my time, I never heard of him). He now works from home as and seems very willing to help. This is what I bought from him. I can t really verify its reliability yet since it hasn t done many miles. IWIS Duplex primary chain, (as used by Mercedes as a diesel cam chain)d67hp x 52e. Pins IWIS Ø4.4mm ReginaØ3.175mm Plate width IWIS 1.4mm Regina 1.4mm Plate height IWIS 9.59mm Regina 8.1mm The IWIS 52 link chain weighs 469 grammes

12 Here I just applied a random load of 1000N to a IWIS link model and a Regina link model for a comparison. IWIS dimensions Regina dimensions

7. The thyristor within the Motoplat, is triggered at 0.8V by a 1Vpulse coming from the trigger coil. The trigger pulse is delivered to the thyristor (within the ignition coil), via the Black wire.

13 7. The thyristor within the Motoplat, is triggered at 0.8V by a 1Vpulse coming from the trigger coil. The trigger pulse is delivered to the thyristor (within the ignition coil), via the Black wire. By shorting out this pulse wave by bridging a 15 Ohm resistor to the Blue wire, you can distort the pulse wave slightly with respect to its amplitude. What this means is that the 0.8V occurs not on the rising edge of the pulse, but slightly round the corner, if you like, where the voltage is about to peak. This has the affect of delaying the timing by roughly 3.5. If this 15 Ohm bridge is integrated into a kill button type arrangement, it could be used as a starting aid, i.e. press a button on the handlebar to bring the resistor into circuit, then release the button once the engine starts. I have tried this and it does work, but I have no idea what would happen if someone held the button in for a longer period. Maybe the trigger coil couldn't handle this 15 Ohm short circuiting, and it might get toasted. The green and yellow arrows are pointing to noise generated by the ignition coil at the instant of capacitor discharge. This indicates the very point of the spark taking place. You can see that it takes places at 0.8 volts on the rising edge of the trigger pulse. A 1000:1 voltage divider circuit was used to record the capacitor charging voltage, so the peak voltage was actually about 230 volts, even though the CH2 dials is set at 0.1v per division. The capacitor charging trace doesn t show capacitor voltage, but only the voltage that charged the capacitor. In other words, although the trace has dropped off below the zero line before ignition takes place, the capacitor will still be sitting at 230 volts when ignition is triggered by the 0.8 volt trigger pulse.

This shows the electronic internals, and how I connected the oscilloscope. The RED square indicates the ignition coil.

14 This is the set up I used, although I could only reach 2000rpm. I had to insulate all the components from the machine table because they were messing up the oscilloscope trace, since they were using a common ground, i.e. the machine table and the oscilloscope earth were both common, since they were connected through the ring main circuit. This shows the electronic internals, and how I connected the oscilloscope. The RED square indicates the ignition coil. By shorting out the coil as described in the previous page, I was just reducing the value of the standard internal resistor 3 as shown in the diagram to the right, since I was simply bridging the two coil terminals with 15 Ohms.

8. I just bought a de-compressor valve, since there wasn't one on my bike. I discovered that there is nothing to stop the valve from self disassembly, other than the spring force.

Not only does it mean it can come apart by itself, but it also means the amount of valve protruding out towards the piston, can vary depending on how far the collar is screwed onto the valve end.

15 8. I just bought a de-compressor valve, since there wasn't one on my bike. I discovered that there is nothing to stop the valve from self disassembly, other than the spring force. I was surprised that the attachment pin wasn't peened over to prevent it coming apart. I simply screwed it off by hand. Not only does it mean it can come apart by itself, but it also means the amount of valve protruding out towards the piston, can vary depending on how far the collar is screwed onto the valve end. If it's screwed on far the valve has a short stroke, and vice versa. Obviously the stroke is determined by how far the lever is pulled by the user, but the valve displacement is also controlled by the collar which acts as an end stop. I know that nobody should be running their valve so close to the piston, but a couple of turns of the collar sends the valve 1.6mm closer to the piston. This is a naff design, so I redesigned and manufactured the main body. The amended design has three features. a. The NYLOK nut acts as a locknut between the valve and the retaining collar. The NYLOK also provides a means to limit the stroke of the valve. No peening is required so the assembly can be easily dismantled if needs be. b. The spring envelope is now longer which means shims can be added to fine tune the spring preload as required. c. The increase in overall body length provides more support for the valve within the body. The hole size through the body is also reduced slightly from standard. This means that the valves axis is less free to float around within the main body. With the standard de-compressor, I could feel the valve outer diameter rubbing along the threads within the barrel, once I pulled the de-compressor lever. I was able to buy a bicycle lever for 4 which has an integrated grub screw to adjust the lever free play. This type of lever lets you easily remove the de-compressor assembly without even having to interrupt the grubscrew that s clamping the cable end into the de-compressor body. (Since modifying and fitting the de-compressor, the bike is so easy to start that the 3.5 of ignition retard, as mentioned in point 7. above, is no longer relevant, to me anyway).

16 Adjust stroke via NYLOK position Adjust preload by adding shim here if necessary Lock NYLOK against collar with thin spanner

18 9. My 440cc Maico bike kick-started perfectly when I bought it, even without a de-compressor. At that stage however I didn't realise there was a 250cc clutch basket fitted to it. Once I replaced the 250cc basket with the proper 440cc basket, the bike became a nightmare to start. It began kicking back regularly. I m still limping! I realised that the only change was the primary drive ratio. I took the timing cover off and proceeded to slowly go through my kick-starting routine. What I discovered was that when I was reaching the bottom of my kicking stroke, my timing marks were just about lining up on my Motoplat. This explained the kicking back. When the 250cc clutch was fitted with its different primary drive ratio, when I reached the bottom of the kick stroke, the timing marks were about 90 AFTER the firing point. That means I was previously following through the firing point, with my kicking force still applied to the kickstart, helping carry the engine over through Top Dead Centre. With this new 440cc clutch basket fitted, the kicking load was just stopping at the same time the ignition was firing, hence it just kicked back. I think anyone with kickback problems should take their timing cover off and have a look at exactly what is going on in there when they go through their kick procedure, (that's if they have a procedure). If they don't have a procedure then I think its just a case of hit or miss, whether the bike starts or not. Another factor since changing to the 440cc clutch, is that during kicking, the crankshaft no longer spins as quick as it did when the 250cc clutch basket was used. That's probably another factor which helped the 250cc basket arrangement start easier.

This means the kickstart receives less of a torsional load when it bottoms out.

19 10. I also think the kickstart is less prone to breaking off, if it is fitted in such a way that the internal quadrant never reaches its endstop. I purposely let my kickstart bottom out on the clutch casing. Although it creates a mark on the casing, it means that the kickstart is bottoming out closer to five o clock instead of half past four. This means the kickstart receives less of a torsional load when it bottoms out. One other benefit, is that this also provides more of a kicking stroke, which creates a greater piston speed, and gets the piston further past the firing point and TDC. This picture shows two images superimposed. One image has the kickstart quadrant bottoming out and the other image has the kickstart bottoming out on the clutch casing. Bottoming out on the quadrant subjects the kickstart to an additional 20% torque. At 135 a go for a kickstart, I m happy to have this mark on my casing.

20 11. Machining / replacing clutch basket rivets. I just made these from malleable mild steel because I didn t know what else to use. I parted them off on the lathe, leaving the small dotted line shown. I then made a riveting dolly with a small hole in its end. The small spigot kept the dolly in place and made riveting easier. I then just buffed the spigot off with a Dremmel when finished. 12. The Maico Clutch... To be continued...

*Some speedometers have these additional electronic connections. If yours does, then remove the smaller slotted screws shown.

*Some speedometers have these additional electronic connections. If yours does, then remove the smaller slotted screws shown. www.odometergears.com 1981-1985 240 Cable-Driven Speedometers (NOT for 1986 and later electronic units) http://www.davebarton.com/240-odometer-repair.html For this set of instructions below, I will not