kevin mcgrath

My Feedback: (1)

While in the air my RCS twin made a rude noise,and even though I cut the throttle immediatley and landed, the engine was seized.As it cooled off the engine would turn over but the compression was totally gone in one cylinder.Upon inspection I found three bad gouges in the piston and the ring came away in two pieces,but it had not rotated past the pin.The liner appears undamaged and there is no sign of over heating.The engine had been carefully broken in and at the time was running Klotz at 40/1.I do not run my engines lean and dont think this one was set too lean at the time.
What are the possibilities? Ill fitting ring? Foreign body sucked into the carb? Other Im not thinking about?
Also can this damage normally be fixed by a new piston and ring?

Thanks

bdtsr

My Feedback: (5)

If you have an inside micrometer, you can mic the cylinder. Check to see if it's not oversized/worn too bad (get bore size from RCS). If it's ok, then hone it and install a new piston and ring. If it's worn out too far, maybe an oversize piston is available from RCS and bore the cylinder (local machine shop, about 15 to 20 bucks) to the next size. Otherwise it's a whole new set for that side. Also make sure none of the bearing cages came apart. A failed ring could have done just as you described.

Boomstriker

Being it was in the air at the time, I doubt it ingested something.
More than likely the ring caught a port edge and broke.
This is common if there isn't enough radius on the top and bottom edges of the ports after honing or port-work.
It can happen too if there isn't enough ring gap and on a lean run the ring will expand into the port.

If the motor was stock, I'd send it in for warranty work.
If you're on you're own, buy a new piston & ring and if the jug doesn't have any deep gouges, hone it and it will run just fine.

Definitely put some more relief on the port edges and check the ring gap to avoid this again.

Kirk

kevin mcgrath

My Feedback: (1)

Thanks to you both.......you are confirming what I thought.
To be accurate RCS came good on the warranty and sent me a new engine immediatley without return of the damaged one.
Im trying to make up my mind whether to return it to them or buy it at a deep discounted price they will give me since they dont market the model any longer,and repair it........parts arent a problem since the 44cc twin is two cylinders of the 22cc single they still sell.......and its available in europe anyway.......