Modern Vespa

Hi,

Currently rebuilding a px200 engine.

I have .35 mm clearance there, should I add a shim ?



There is a groove where the oil seal goes, I believe some plastic seals have a groove but I don't, I have a metal and a plastic one, which one will fit better ?




Does the oil seal goes this way or the other ?



Thanks !

Yes, Shim.
Plastic.
Spring inside.

Thanks !

what does that crank bearing bottom against again? do they make shims for that or is it just that the bearing needs to be driven home more?

The other way round then ?
Just to make sure

You have a groove in your cases. Unusual in modern cases but who knows what they used to get up to in Pontedera on Friday afternoons.
This needs a rubber seal. Ideally a brown one.
https://www.ebay.co.uk/itm/165589140427

https://www.sip-scootershop.com/en/product/spacer-bearing-crankshaft-clutch-side-o-50x62-mm-th-0-3mm_90012013

springs towards crank

I was talking about the rear shaft one !

I know ideally I need a grooved seal but I don't have any , is it that important or can I go with the flat plastic one

I'm sorry.... as Jack said, towards the inside ( of the case).

The seal will expand into the channel, forming that groove you'll see on used rubber seals. New, they're smooth.

Shim in this manner, at around 4:15 here.
Ignore the metal seal part.

My 77 200 also has the groove for the seal. I find seating the bearing is less precise than on the PX cases. The clutch side of my case there are studs for 2 tabs that the bearing bottoms out on as well as a groove inside the case and also on the clutch side for fitting a circlips. I had to adjust the bearing a little with a punch to align the crank after I put it in.

What does the bearing look like from the clutch side of the case?

I think I tapped the bearing a bit too hard, the circlip on the clutch side did bend a little bit, hopefully the aluminium did not crack ! I pushed back the bearing the other way and with a flat circlip the tolerance is out .10 mm.

For security I'll replace the clutch side bearing circlip.

It is not easy to properly put on as my circlip plier does not open wide enough. This is only circlip in the engine requiring a large circlip plier