To Fix the Kreidler 'Shaking' Problem
1. Buy ATF Type-F transmission fluid.
2. Drain the Kreidler transmission-- the plug is on the bottom of the engine, it might be a 18mm or 17mm socket.
3. Take out the screws on the tranny side cover carefully.
4. Remove the tranny cover gasket CAREFULLY-- it is a bitch and a half to make a new one.
5. Remove the shims from the two shafts that stick out (small, thin washers).
6. Buy more shims if necessary.
Shims Purchase Page (Shims are there, but they come from the Netherlands. I have ordered from them a few days ago, but didn't get an invoice as of yet)
- I have all .1mm shims, I'm not sure if the other thicknesses would be useful**
7. Place two shims on each shaft to start off. (This should be ideal)
8. Put everything back together, without fluid, and start it up. See if the engine will idle with the wheel touching the ground. If not, you have too many shims! Take one out at a time, experiment and see what will let your engine idle. You can safely go around the block if you're careful.
9. This should work! I believe it also depends on the thickness of your tranny cover gasket-- but not by much.
If this doesn't work, find someone who has a spare side cover to try. I get the impression that the bearings in the tranny cover wear out / get loose / misalign after years of use, and thus create the imbalance that causes the engine to shake while shifting. Optionally, you could also try replacing the bearings in the side cover, as well as the needle bearing where the clutch sits.
The output bearing (shaft that connects the front sprocket) should also be replaced! This will help with alignment / wear issues inside the transmission.