Sounds like a piston/ring problem. You should send it in for service. This is a tell tale sign or a scratched liner, or warped piston, or it could be just a well worn out ring.

I would suggest to you that prop is probably too much load. You need to run the 140L about 8200-RPM I would prefer above 8400 personally.

But if you given prop was turning that proper rpm..then you are fine. Overloading the engine down into the mid to low 7000's will in effect overheat it and could cause the problems you are describing. Or it could have just eaten a rock or some other debris and scratched the liner.

It is in need of service for sure.


Troy Newman
Team YS