Urgent!!! Need Help

[gotsand400]

PUTTING MY 440 KIT IN AND I DON'T REMEMBER
IF THERE WAS A O-RING ON THE BOTTOM OF MY
CYLINDER. AND I DON'T HAVE ONE , WILL IT HURT
ANYTHING. I NEED TO KNOW.

[gotsand400]

I HAVE THE GASKET, BUT THE BOOK SAYS IT ALSO
TAKES AN O-RING

Stop! I am in the exact place your in my 440 rebuild and I was told to go and get that o ring. They sell for $6 at Honda and there is a reason for them. ( I don't know what) I assume it is to ensure no vaccuum leaks in the low end of the motor. I strongly recommend that you wait and get a new one. It would be a shame to risk your brand new motor over $6.;)

[MIKE400EX]

Maybe not the intended reasons for the o-ring, but 3 that come to mind.... 1. You don't want oil to work it's way between the sleeve and jug when they expand and contract. Gradual buildup of even a film of deposits/varnish could pinch the sleeve and tighten up the piston clearance. 2. The rubber o-ring may act to attenuate vibration of the portion of the sleeve that protrudes from the jug, thereby reducing risk of cracking and subsequent failure. 3. The better the o-ring seals the cylinder assembly to the cases, the less cycling pressure the base gasket will have to deal with.

[cals400ex]

will that same o-ring fit on a larger sleeve though?

Yes it fits, I just put mine on my new weisco 440 sleeve and installed the jug on my bike.;)