Modern Vespa

Hello all
I replaced the 'wrong' metal clutch side oil seal with the correct ridged Viton type (early P200Es have this type). This was after the previous seal gave way (ethanol?). Since then, starting has been difficult at best and running very intermittent. Great spark, compression, and fuel flow to the carb (I've cleaned and rebuilt two carbs: both sit flat and secure: no leaks). I have been getting what I believe are 'dry backfires' through the carb.
The shoulder for the seal has been damaged in the past but was serviceable when I bought the bike 15 years ago. All issues have come since replacing the dead seal.
I have attached a picture of the damaged casing. I'd like to know if anyone has experience of a leak like this (if it is a leak) and rebuilding the case with some chemical metal (I'm not a fan but needs must).
Thanks in advance, Peter

Peter,
First thing to do is to confirm your seal is leaking through a pressure test.
This is different than compression and involves sealing the carb entry and exhaust port off, while pumping 5lb of pressure into the case.
Easy to search these pages for a how to if not familiar.

If your seal is leaking, a replacement using loctite should help significantly. Someone else can chime in here with the loctite type number.

Let us know if you've already tried both these things.

Hi

Thanks for that. I'll order up a new seal and go again.

No pressure test yet as I was expecting to find a 'rapid unscheduled disassembly' when I tore in to it.

I'll do it on reassembly.

I'm guessing Blue Loctite 242 should work. Unless anyone knows any different.

I will make sure to keep this updated.

Thanks, Peter

Most the guys use 603.
Many swear by it.
Suspect it will do the trick for you.
Pressure test is essential - no matter how careful you think you've been - leaks are common for all of us.

Yes, 603 is good. I just wasn't sure about using it on the Viton not-rubber. I'll ask the supplier.

Back to the first question: it sounds as if you think that the Loctite should seal around the damaged areas. It does claim 'filling' properties.

I'm not a huge fan of trying to fill the gaps with JB Weld or anything like that. It's just as likely to come adrift and repeat the damage.

I've just picked up a cheap Sphygmomanometer on eBay. Just need to get rid of the stethoscope that comes with it now.

And incase anyone else travels this way: two links to SLUK videos that are relevant.

1. TEST BEFORE YOU STRIP:
2. BUDGET PRESSURE TESTING:
More to come I suspect.