Piston Question?

[bubbag]

Hello,
I blew my headgasket riding my R the other day but now that I popped the head off I can wiggle the piston around in the cylinder but it still did a compression test of 150lbs with the head still on? the cylinder doesn't have any scratchs in it, and everything looks good?
Should a piston move a little bit? when it is at the top of the cylinder?

Thanks
Bubba

[kfxwizzard400]

yea it should maybe replace your rings just in casehttp://

[xlr810]

It is normal for the piston to move inside the bore a small amount. However, the rings should never leave the surface of the bore. You should really take the jug off and measure the difference in diameter between the piston and the bore. Also measure the ring end gap.

150 pounds compression is pretty low. Best case scenario is that you need new rings. Might as well replace the wrist pin and wrist pin bearing too, if you go that route.

More than likely it is time to bore it up to the next oversize and go with a new piston kit.

Just installing a thinner head gasket to increase compression is not doing your motor any favors. Loose components lead to excessive piston slap. Let that go, and you might need to replace parts in the lower end, too.