Breaking in a new 90 sized ABC engine, about one gallon through, all on test stand, I am at WOT and hear a clattering racket in the engine. Shut it down, remove from stand, remove muffler, look in the exhaust port and see a lot of aluminum debris. Remove the cylinder head and look down into something like a gravel pit. A piece of aluminum has broken off from somewhere internally and gone into the upper chamber, where it broke up and partially melted around the jagged edges, sort of like river stone. Remove backplate, see nothing amiss in the lower end, no aluminum appears to be missing from the piston skirt. Sent it back to service department for them to figure out. Total mass of the debris amounts to maybe a pea-sized piece of metal.

I don't want to mention manufacturer, because I am not inclined to think it is a problem with this particular brand. Just curious whether anyone else has had something like this, and did you ever figure out what it was?

did you do a hot break in

I have had similar problems with OS engines so i'm wondering if your new engine was an os. I fly mostly smaller engines though.
If you search the problem of peeling liners in RCU all threads point to os which has been having an ongoing problem with this. I actually like the brand but am tired of changing the piston and liner every season. Even though they stand behind the product I just don't think it's necessary to have to do that. I have started to sell my OS's and replace them with other brands.
So to ask, is your engine is question an OS?

If there was a good pea sized chunk of shiny aluminum debris in the engine its not a peeling liner. The liner would flake off in pieces so small it would appear like dust (if you could even see it) and the liner material is dark grayish in color. Also, you would see exposed brass on the sleeve.

Its funny how OS continues to get bashed for peeling liners on all of their engines. I though the problem was only the .46 and solved a couple years ago? For what its worth, I have a 46FX bought about 2 yr ago and have had zero liner problems with it. I run it hard too - 11x5 turning about 13-13.5k on a fun fly.

Just MHO. Flame suit on.

Jeremy

I've seen something similar in an OS 46 that blew it's rear bearing. The cage breaks, balls fall out and play squash for a while on top of the piston

Majortom,

This is one instance when you need to exercise your warranty.
Just take your engine to the LHS, or whoever sold it to you and get a replacement free of charge.

I have seen all kinds of machining junk inside an engine, which will make your engine very old, before the break-in is even through.

Just so you don't trash the replacement as well, remove the head and the backplate, just before mounting your engine on the test stand for break-in. Wash it out with methanol and verify no particle, aluminium, steel, brass, or chrome is in the engine.

Oil and reassemble the engine properly and perform the break-in in accordance with this thread:

http://www.rcuniverse.com/showthread...59&forumid=145

Sincerely,,

Hey bugsiegel, how do you manage to flake the
lining off your os engines? I have had four
fo these engines and they all run. One that I
have has well over three hundred flights and
still starts without a starter. I think the
main problem with the flaking is running to lean.
Run ti a little richer and I bet you won't have
any more problems.

Not OS, definitely not liner flaking. Broken in with short runs at WOT, rich two-cycle needle setting. Engine ran well through a gallon before it failed.