Possibly a bent crank shaft. Could it have gotten bent in shipping....I had this happen to one engine...

Could it be that the engine mount is not strong enough in the firewall...or could it be a bad bolts....I just don't know there are many options.

All I can say is to send it for service...If it just came back from service as in YS Parts and Service....then the engine was run and operating correctly when it left Nevada.

If the engine is running really rich it will vibrate more....but I doubt it would break mounting bolts.

If the prop is not balanced or perhaps the crankshaft is bent it could vibrate enough to cause this problem. If the crank was bent when it was sent into service, it could have been missed but I would doubt that....The engines are run by the folks at YS Parts and Service in Nevada (USA) so when they ran it they would have seen the prop shaft bent....

I just don't know what to give for advice on how to fix it. I suspect the prop is out of balance. Perhaps the mounting bolts were too tight, perhaps they were not tight enough. Its just too big of range to speculate on a cause.


Troy Newman
Team YS