Modern Vespa

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

How are you pulling the crank into the clutch side bearing? Are you using a crank puller?

I don't know If I would trust runout of a crankshaft if only one side secured. You can remove the crankshaft and check for runout using a veeblock. Adjusting a crank is not too bad and you can find youtube videos on it.

It's more likely that one of the bearings isn't seated correctly than the crank itself is out of alignment.

Normally the bearings are installed on the crank first, the crank is pulled into the clutchside, then the flyside case half is heated and installed. Is that how you did it?

Many thanks Captcha and SoCalGuy for your responses.

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

Chris - when you pull the crank out - if the bearing stays in the case on the clutch side - perhaps shoot a picture for us so we can see how its sitting.
There is a brass seat that the bearing sits in - you may want to have a very close inspection of that.
Pay attention to its edges to see if they are completely flush 360 degrees or if there is a low side.
If you do have a low side - look at the cases to see if there is a commensurate marking from the crank.

The other place that you can get interference would be the inlet pad - as this is the closest clearance spot.
You should be able to slip a feeler gauge in between the crank and that pad to measure clearance.
Did you do any repair of the inlet pad?

Thanks charlieman22 for the comments.

i will try add some photos. I suspect the bearing will come away from the crankcase with the crank when i remove it, it did that first time.

i will carefully check the brass bearing seat all round.

i'm not sure what you mean by "inlet pad" - can you explain more?

cheers

Chris

when this happens I usually get the puller on the clutch side again (with cases closed) and tweak it all up hoping to get a few more mm towards you....the tool should pull both the bearing square and the crank in further.....BUT.... dont force it too hard...feeeeeel it move or stop

Better to open it up. seat the bearing so you get a good visual that it is flat in the cases and then pull the crank through

Once, a good tap on the fly wheel side did the trick

likely conclusion....bearing not seated square....now up to you how to proceed...either gentle, well meaning, well placed force or split ye must

good luck

Thanks Bluecati - the overall opinion is my bearing not seated correctly. I'm very grateful.

By the way my original post should have read 10thou not 10" !!!!

Chris

If it's the original 152L2 motor you are building there is no inlet pad, as they are piston ported, with the inlet on the cylinder.

yes, it's an original 152L2 engine, cheers