ORIGINAL: RCIGN1
Sounds like the bolts were loose..A 19 pitch is way too much for a 44 twin..No wonder the top rpm is 5500..We use a prop like that on our 80cc racers..If a spark plug blew out it had to be loose, too...Was the engine new ? Maybe you should send it back to RCS.......
Black "stuff" sounds like aluminum wearing on aluminum, maybe it scuffed a piston when the prop bolts sheared.....
It was a typo on the prop size. It should be 22-10 cut down to 20".
The engine is about 1 year old with about three gals thru it.
Thanks for your input.
I expect the prop bolts were loose. I had put in a spacer to clear the cowl and the bolts only penetrated the back plate about 3/16 of an inch. I should have rechecked them after the first flight but forgot to.
I don't know how the spark plugs got loose though. They were clamped in the boot with a hose clamp around it. I think DKjens is right- that head does not have enough metal in it.
I have not been able to get much out of RCS lately. I think they don't monitor their computer anymore. I would not like to have to send the engine back to them. I have heard of people waiting long periods for the return of their engine
I finally got an answer from RCS- they want $30 for a new head. That seems reasonable.