dirtybird

My Feedback: (5)

I have a question for the engine guru's of this forum.
I have an RCS44B2 (Moki) twin.
In the first flights of a new 83" Fly Baby bipe I just completed, I lost the prop. Four of the six mounting bolts were missing and two sheared. The engine quit before I could actuate the cut off.
The next day, after replacing the prop and bolts, the engine ran ok for a few minutes, then blew the spark plug out of one of the heads. I replaced the head with one from an RCS140 that has the same cylinder as the twin. I had a lot of trouble getting a seal at the new head.
Now the engine will run OK at top speed but I cannot get it to idle at less than 2500rpm. There seems to be a lot of black stuff coming out of the exhaust. The throttle cuts the speed when it is reduced only about 1/2 of what it previously took for the idle.
I am using 50:1 oil mix with Penzoil 2 stroke oil. The prop is a 22-19 Zinger cut down to 20". I get about 5500rpm at top speed.
Do you think it should be torn down and examined? What should I look for?
I hate to take it apart- there are a lot of screws in that engine.

Antique

My Feedback: (4)

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.....

DKjens

My Feedback: (50)

Is a 50:1 oil mix enough for run in? I had one of these engines for a moment at one time, there really is not much material in the heads where the spark plugs screw in, it is a crap shoot to tighten them enough, but not tear out the threads.
DKjens

gunny11

My Feedback: (6)

Does anyone have this engine and is running with good success. I have two NIB. Does anyone know the torque specifications on the spark plugs and the prop bolts?

Thanks

Gunny

dirtybird

My Feedback: (5)

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.