I read from a lawncare forum that the 4 cycle Honda GX31 31cc engine have vibration problem at top RPM. The vibration were so bad that it actually crack the crankcase!!! Anyone have experience of this problem on the unmodified engine only. I can understand if you modify the engine, you are pushing it to the limit. But for an unmodified engine, it is hard to believe it would do this. Any comments?

Is the GX31 design robust or the GX35 is better?
Thanks

While I haven't had my 31 in a plane I have run it plenty and never had vibration issues. I know there are guys on a boat forum that hot rod these things and run them at 10,000 RPM with no issues.

Thanks Tim220225
That make me feel a whole lot better! I don't think Honda will make something like that. It is a very popular engine for equipments.

BTW since you have experience with this engine, can you tell me whether it has any cylinder wall lining or just plain aluminum? Does the connecting rod have needle bearing on both ends? I have trouble getting a clear break out diagram for the engine.

Thanks