Hey guys, Ive never split the cases on an EVO before. Ive developed a decent leak from where the cases meet. It happens after shutdown when the engine is hot, and my driveway is paying the price!! Ive broken down the microfiches and it looks like there isnt a seal between the cases? Is it just the machined surfaces?


Not looking forward to tackling this one!!!! Damnit.

 

You are correct .... There is no oil type seal or gasket between the cases. The cases are sealed with a sealant ... not sure if HD makes one specifically but I use to use ( don't hate on me ) Yamabond ( yes Yamaha from the people who brought us Pearl Harbor ) and it worked great ... Be sure that you are correct on your diagnosis as to where the leak is coming from .... it is common for EVO's to leak from the base gasket ( especially rear base gasket ) .... you might check to ensure that all the case bolts are tightened to specs before tearing it apart also ... case leaks are not a real common problem.

 

Sh*t, thats what I thought. Thanks Larry. My diagnosis is 100% unfortunately. I figured they used a sealant because after inspecting for the leak I found a string of "Silicone" type sealant hanging down from where the cases meet....exactly where the leak is. My base gaskets each have very small leaks, more of a weep that I dont worry about. This leak is a little more substantial though and something that is going to have to be dealt with. Im going to re-torque the case bolts as well.

Hopefully it will not worsen and I can make it til next winter just adding oil when necessary. Then the engine is either going for a full HD reman...or Ill go the S&S/Ultima route.

 

Just clean the area outside or the case and seal it from the outside, it will work ....but I would use some industrial sealant, I have a 3m number st home, I will post it later

 

You know that crossed my mind but I figured it would be pointless. I didnt think anything would actually seal it just applied to the outside.

 

Just a guess here, but I'd say sealing from the outside should have some success if the area is cleaned exceptionally well. Since it's a dry sump system and there is very little oil pressure. I'm a car guy, so I'm looking at it in car terms, but principles are principles. I've used Permatex gasket shellac to stop a water leak, applied to the outside of a cracked thermostat housing and it worked. Was an emergency at the drag strip.
I've seen people have some success with outside sealing of the jug bases too.

 

Hey, its worth a shot. Ill clean it up really well with some brake cleaner and then run some RTV down the seam.

 

Do not use brake clean, use starter fluid and a higher end sealant or this won't work .

 

Man, I use Permatex when assembling engines?!?! What would you suggest?

 

I feel bad for you that the cases are leaking, I had my bottom end rebuilt by an indy here, if bottom end didn't need work I probably would have split the cases myself, a bit intimidating but a couple of my buddies said there's nothing to it. I hope you can take pics and if your successful as this is a biggy for all.I have heard HYLOMAR UNIVERSAL GASKET DRESSING is very good stuff and althogh I have some on the shelf I'm never had an opportunity to use it as I tend to use gasgacinch with the gaskets more and no call for a sealent.