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I need some expertise on this. I am reassembling my engine (1st time) and using a supposedly stock gasket kit. The o-rings included for the cylinders are about 0.008" larger in the minor diameter than the ones that came on the bike when it was new (0.078 vs 0.086"). The o-rings do not fit down into the grooves like the originals and when it is reassembled, the cylinder kind of "floats" on the crankcase; not fully seating on the crankcase. I'm not sure if I should just go ahead and torque it down or put the old o-rings back in for a better fit but questionable seal.
 

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I would go ahead and torque it down. The only other option I would consider is getting another set of sealing rings and measuring them to see if they're different, but I wouldn't pull the cylinders off till I knew I had something that fit better than what's already on. Besides, they're made of rubber, they will conform. I would use a light coat of vaseline on the ring if you can lift the jugs high enough to get some on, that will allow the ring to not get pinched under pressure.
But I'm no expert either.


FR
 

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I just ran into the exact same issue when rebuilding the top-end of my CB350. Having destroyed the old o-rings while removing them, I used the new o-rings. I used Permatex High-Tack gasket sealant on the cylinder base gasket as well. It comes in a little metal can and it's great stuff, though nasty to work with. I only have a few hundred miles on the motor since I got it back together, but there's no sign of any sort of leakage.
 
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