[Perpetualrepair]

Hi, I have a brand new OS61FX I ran it in as per the instructions, on 15% fuel,
it had a mid range knock all through the run in, now I have it in a 4*60 and it makes a real bad knocking noise in the mid range, transitions well revs to the Manufacturers specs,
Any ideas on what is happening, should I return it or is there a cure. Thanks.

[Wayne MIller]

Hi,

If your engine is mechanicaly OK you may want to try another muffler.

I had the same problem with a 46 and was very concerned. Our "engine person" at the field said it was normal and was caused by the muffler - I was suspicious and changed to another muffler I had kicking around to test - the noise went away - I went back to the original muffler, had the same noise, and the noise went away after the engine was broken in.

This may not be the case for your engine, but you may want to try another muffler just to see.

Hope this helps.

Fly4Fun,

Wayne

[3dflyer]

i would take out the backpressure plate out of the muffler.i haven,t had a problem like you got,but i would remove it and see if your problem goes away.hope this helps.

[Dig it]

If the needles are set to factory defaults then it simply isn't set for your altitude. Factory is a good start, but by no means where it will run perfectly.