Modern Vespa

I have heard a few people recommend using a little locktite on the clutchside seal where it meets the crankcase. I can see how this may be helpful with the metal seals but what about the rubber seals? Do you use it and if so, do you just put a little smear of it on the edge before pressing into the case? I've been building these things for close to 40 years but can always learn something new.

That would really depend on what cases you are putting it into

the rubber seals ideally need to be placed in the cases with the small recessed machined ring.

But as you state you have many years of experience here i am probably telling you what you already know, i'm just saying this for those that read this thread and don't know the differences.

so YES, any extra help you can give a seal to stay in place is a good thing (given there prevalence to spin out on high mileage or tuned motors.)

Forgive my ignorance about the Loctite, but I'm a bit leery of Loctite-ing rubber on metal. Didn't even know that was possible. What # Loctite would be appropriate for that purpose?

I've been using LocTite 603 on both metal and rubber seals for a couple of years now. Works great.

Chandler, do you have any thoughts on using the "overseas" Loctite that's available on ebay? It keeps enticing me, but I keep thinking that it's probably "bodge in a bottle".

I would not trust the eBay supply chain for things like chemicals. It's almost certainly just dyed cyanoacrylate, which will seem like it worked, but in reality will break down pretty quickly when exposed to heat, gasoline, etc.

The reason chemicals like this cost what they do is because that's what they cost to make. There is enough competition in the market that it's pretty heavily commoditized. Thus, there's not a lot of excess profit to be undercut in an ebay sale, unless the seller is stealing cases of it from work or something.

Besides, even that tiny bottle isn't that expensive, and will last you through many rebuilds

Do you want some legit Loctite 603? We did campaigns at work that required a literal drop, they gave us a bottle every time. PM me your address, I have a few left.

I believe people use Loctite 515 or Permatex gasket eliminator stuff.

So it is more like installing a gasket rather than locking something in place, as in Loctite bearing Fit

Aha, thanks for that offer Ape but I've already got a bottle of the 603. Didn't realize it could work on the rubber-edged seal. (It's such noxious-smelling weird science going on in that green stuff that I just assumed it would eat through rubber.)

Then again waspmike suggests some 515 gasketing material instead. I wonder which is better.

Nope problem happy to help! Will admit though all my 603 has grown lega apparently and didn't have any actual Loctite 603. BUT, doing some research and a cheaper option is Permatex 64000. Much cheaper than Loctite and will work just as well.

https://www.amazon.com/dp/B000HBIDME?tag=duckduckgo-exp-b-20&linkCode=osi&th=1&psc=1

I use Loctite 648 on metal seals, and I use those metal viton seals on all my scoots, with or without the groove. If your engine has any degree of compression, rubber seals can pop out, and I've had metal seals spin. Metal seals + 648 have eliminated such issues hopefully forever.