Crank seal installation

[2T5]

Hi all,

I've just disassembled a bottom end (2 stroke MX bike) due to a suspected clutch side crank seal or crankcase join leak.

When removing the crank seal, it seemed to come out without much effort and can be fairly easily reinstalled by hand with no tools. Should I be concerned by that?

I have measured both the old and new seal (genuine Yamaha) and they are almost identical in diameter and are approximately .024" (.6mm) larger than the crankcase.

Is a sealant like Threebond an option to apply to the mating surfaces when fitting the new seal?

The removed seal is only ten hours old.

[Economy Cycle John]

Fit them dry and do a leak down test, only way to know for sure. Pressurize to 6lbs, no more than 1lb per minute loss.   

[2T5]

Thanks for the tips.