does anyone know what material if any is used to seal up in between the engine cases before the halves are put back together? ive got em apart for a repair and found some sort of silicone. what would i use when reassembling them? thanx in advance.

 

The factory uses a .015" bead of silicone based material, that minimizes the amount that is squeezed into the case. Any silicone that is squeezed into the case can come loose and go where it shouldn't. We use Hypalomar non-hardening sealant, that way if any gets into the case is is fluid enough to mix with the oil and cause no harm. Hope this helps.

 

Silicone is the factory stuff on the later ones. They used to use Permatex #2 years ago.

I used Hylomar on the last one I did, and thank god it was mine... I've had to use copper washers on 3 of the thru bolts (not fitment studs) to stop leaks I've done dozens with silicone with no problems.

I mean think about it: it washes out with hot oil... so you're trying to ensure a leak free seal on any minut imperfection in the case surfaces. If it doesn't squueze out, then it's somewhere that it is supposed to be sealing something, right? Well, if any hot oil washes it out from an imperfection - it will leak, and I will attest to that, first-hand.

And please do not think I'm trying to discredit John in any way. He does it for a living and knows his stuff. I just hobby at it but take great pride in my work, nonetheless. So John, I sincerely wish you luck on all the ones you've used it on. Splitting cases under warranty for a leak like that is very anti-profitable, I know.

 

I use Grey Permatex.Avaliable at any parts store and it works.Jap car/bike makers have been using it for years on there stuff.As for hylomar,not no but hell no.That stuff works great on cork gaskets but for sealing cases no so good.A older tech at the H-D shop i used to work at swears by it "its all we ever used back in day" But he also swore at it when he had resplit the cases for yet another case leak.But now times have changed as well as technology,ive put together quite a few engines with the grey permatex (car and motorcycle),and so far ive had absolutley no problems at all.
However be sure to use a small amt,as you dont want it getting in oil passages or the oil pump.

 

So far so good, no leaks with it (knock on wood). If you put it on too thick you can have problems. I just got tired of waiting for the silicone to harden so that we could go inside the cases and pick out the RTV that seeped in. We've pulled apart engines that had cranks scissor after 10-15,000 miles and the Hylomar was setting there smiling at us. We only use the 3M hylomar and it's getting hard to find around here. There is some no name brand hylomar out there that they use for plumbing. We bought a tube of it and it is much thinner than the 3M brand, and we don't use it

 

I really never gave a thought to the possibility of different formulas by various manufacturers. It said right on the tube- "flange sealant" so who was I to question that? I used Permatex branded and clearly, there IS a difference between mfgs.

After all this, maybe I should go throw out my thread locking compounds by anyone other than genuine Loctite... and check the expiration dates on what's left

 

Does anyone use Yamabond anymore?