New shims for ZA 50 engine

Do you need to replace engine shims if you change bearings and seals on this engine? And are they available anywhere or not? Can you merely use the same ones again (if you're careful)?

Re: New shims for ZA 50 engine

As long as the thickness is still correct, yes.

Re: New shims for ZA 50 engine

What would change the "Thickness?" I don't understand that comment. If you are removing a bearing and a seal and replacing same with same, how does "thickness" issue play? You lost me.

Re: New shims for ZA 50 engine

Very seldom will you get a bearing that is exactly the same as the one you are replacing.

Although tolerances are tight they're not perfect. The shims allow for end play on the shafts, to help align gears, etc.

Not enough end play and you end up with a shaft boring it's way through the case, if it will turn at all. Too much play and you get lateral movement which can cause wear in meshing gears,noise, or binding.

The repair manual for this engine shows a complicated process of determining the proper thickness for the shaft shims using special measuring tools. Even the thickness of the case gasket is critical. The manual cautions you to be sure to use a new gasket on the case mating surface before taking measurements.

Look into a product called plastigauge. It is a plastic material which when compressed retains it's compressed thickness.

You can cut a little piece and put it between the shaft end and the case. Then assemble the case with the gasket and torque the case bolts evenly. Disassemble the case remove the plastigauge and measure the thickness with a micrometer. Find out the recommended clearance and subtract this number from your plastigauge measurement. The difference will be your shim thickness.


Re: New shims for ZA 50 engine

Than you Tim for precision reply. What if you had a "supply" of the same # bearings and checked until you matched one exactly to the same thickness of the existing bearing? Do you think that would eliminate the tolerance issues and allow you to use the same shims? So far, I haven't gotten any answers about where to find these shims for the two speed.

P.S. How is your project progressing changing from a one to two speed Puch engine?

Re: New shims for ZA 50 engine

Same question, again, as immediately above.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account