Vespa 152L2 1959 - bent/misaligned crankshaft assembly?

[chrisbwy]

Hi All,

You might have read my previous posts re my non-starting 152L2.

I decided to split the crankcases and replace the two seals, plus gasket.

I have also fitted new bearings whilst it was apart.

The clutch side of the crankshaft assembly is back in place. But when I bring together the flywheel side then the rotation of the crank starts to tighten up, finally ceasing altogether.

The two halves of the crank case do actually meet ok with minimal effort. But I then can't turn the crank, it's solid.

I've removed the flywheel side again and the crank is free to rotate. I made a very rough measurement using a neighbour's dial gauge and stand and got a total of about 10" run out.

This is the first time I've split a Vespa engine and after much reading, it appears that Vespa crankwebs are quite delicate (compared to the British bike stuff I'm used to). So I suspect I've been too heavy handed or have done the procedure in the wrong order.

I think the clutch side bearing and that side of the crank assembly are fully home in the crank case, from the best of my ability.

Do you think my only course of action is to remove the whole assembly and find somebody to check it and true it up if necessary?

Any comments much appreciated.

I have posted this elsewhere - so apologies if you're reading it twice.

Thanks

Chris

[alan34]

Hello everyone.chris sounds defenatly like crank or bearings to wide try measuring bearing width with old ones let us know how you get on cheers alan

[chrisbwy]

From my investigations and your comments (plus those of others) it sounds like the clutch side bearing is not seated uniformly.

My method of rebuild was wrong too - first time and I didn't do enough reading up!

I put the new bearing on the clutch side of the crankshaft, then pulled both bearing and crank through the clutch crankcase side.

Sounds like I should have seated the bearing first so I could visually see what was going on. Then passed the crankshaft through the newly seated bearing and pulled it in.

I also had a close inspection of the bearing last night through the two big holes in clutch side crankweb and I'm quite certain that at one side of the bearing it's flush with the crankcase and at the other side there's a slight step - indicating it's not seated uniformly.

So that's my Easter task. After I try that technique, if the crank binds when the two halves of the crankcase are mated again, then I'll have to assume the crank is bent/misaligned too. But at the moment I'll assume it's ok and that the clutch side bearing not being seated is my only issue.

I'll post an update next week.

Cheers

Chris

[alan34]

Hello there regarding bearing. on my 2006 px there is a circlip then the bearing and oil seal. Be careful putting oil seal in I didnt get mine straight the first time had to order another this is on clutch side.it goes circlip. bearing. oil seal. then crank. keep seeking advice if you are not sure good luck cheers alan.

[kru251]

Mar 29, 2021 15:04:45 GMT chrisbwy said:

Hi I made a very rough measurement using a neighbour's dial gauge and stand and got a total of about 10" run out.

Chris

Errr, ten inches of runout? Probably not eh? Ha ha
Or ten thou?

It does seem to point to an incorrectly seated bearing from what you stated anout it tightening up as the two crankcase halves are reunited!

[chrisbwy]

Glad somebody's read my original post in detail

Yes sorry 10thou

Thanks for the additional comments everybody.