Base Gasket wont seal on new rebuild

[t_mihalenko]

Base Gasket wont seal on 2003 RM 250 new rebuild. I have tore the bike down again and replaced the stock base gasket with a aftermarket base gasket. Got the bike all back together and it still barely leaks. The bike is producing around 245lbs compression.


I would really appreciate it if someone can help. I don't understand why im having this problem. The whole engine is brand new. New weisco piston, crank, L,A, Sleeve cylinder work, bearings etc...

 

[Jon K.]

245# sound high to anyone else?

I had an old Husky 390 that would not keep a base gasket at all. I found that the bottom of the cylinder had a sort of radius at the corner of the base gasket surface and the sleeve area. This radius would snug up against the cases, and the cylinder would not tighten at the mating surfaces.

I had to chuck the cylinder up in the lathe, and machine this radius out.

t_mihalenko; why all the engine work?

 

[reelrazor]

Yeah, 245# seems high to me. Something is warped or distorted, no doubt. It shouldn't be that hard to get a seal with a decent aftermarket or OEM gasket.

 

[t_mihalenko]

I think there's so much compression because when I sent the cylinder to L.A. Sleeve they had to Deck the cylinder then cut new O ring grooves. They milled quite bit off. How can something be warped or distorted if everything is basically brand new?

 

[reelrazor]

The case surface may not be flat. The cylinder can and will distort if its' bolts aren't torqued right. They(L.A. sleeve or whoever installed the sleeve) may have screwed up. The people who I have sleeve my stuff(shop jobs) will only deck the sleeve down to the cylinder and make sure it is flush. With 50 or 60 cylinders this last year alone not once have they had to re-cut the o-ring grooves(at least not all the way) .

Did 'they' specify that you needed to double up on the base gaskets? Or use a thicker head gasket?

I would be hot if I sent out a set of sled cylinders, like a triple, and they sent me back parts that now require race gas.