Ive been fooling around with this engine a bit

Its done about 2 gallons in a heli


and then about 1 gallon in a plane



and I put it back in a heli with the aeroplane head


and its not tuning all that good getting a little lean

Im getting a heli head ,

Looking at the cylinder wear


the ring is not touching the top of the bore in a couple of spots ,

that cylinder is not all that round

so its not really the head that is sending it lean


its the really non existant compression

What can I do


















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Not to sound flippant, but throw it away and get an OS37

Ring and/or cyl?  I would try adding more castor in the fuel just to seal a bit better. It is cheaper and easier than a new ring. (no I am not one of those castor fans, more of any synthetic oil may work too)

Ive got 20% castor in now , Its not tuning bad considering the lack of compression Im tempted to just run it to round up the cyl

Its not cutting out

Maybe its like an Enya and needs heaps of running to run it in

That cylinder is so out of round its remarkable

what are TT doing ????

Your factory piston ring might just suck and should be replaced with a Frank Bowman ring. Not all rings are created equal. Some imported rings take forever and eternity to break in and seat, if they ever do. Maybe TT used a crappy ring in that engine?

Did you get it used or NIB?

Also, could you post a picture of the inside of the liner where you say it's out of round?

That particular model of helicopter engine, unlike most of Thunder Tiger's otherwise excellent products, isn't normally held in high regard by most helicopter pilots. Maybe a new ring or flying it more will improve it, but you might be time and fuel ahead to just replace it.

MECOA and ASP both offer .46 heli engines for under $100, so I don't know that I'd be all that willing to spend a lot of time messing around with a TT .39 that has a weirdly shaped cylinder. Good luck and good shopping!

I will fly it a bit more and report,

I have never heard of one peeling the nickel ,


so I think Im safe there


its got new bearings in about 8 flights ago

Will give it another gallon that should build up a bit more compression

One good thing about the TT is that the starter turns over very fast, and parts are cheap , Ive done a lot of work on the carbarooster, and other secret mods , to get to get it


to motivate so I dont want to waste that , and I have a large volume muffler coming

that Im making


so if the ring can round up all be very good

Put a couple more tanks thru usual heli problems balance and close calls

Its quite powerful

and holds its tune well,

Ive done a lot of work with the idle needle as it affect up to 80% of the range

still can turn it over prop nut style with thumb and little finger,

you dont really need compression <br type="_moz" />