Thunder Tiger 39 vibration

A buddy of mine just replaced his 39H with an OS 37. He did this because the vibration from the engine was so bad that it caused foaming in the fuel tank which in turn leaned out the engine. Is this normal operation for this engine? This guy knows his stuff too. He's been flying helis for the last 20 years. Oh, the engine came in a raptor 30v2 ARF. He put the OS in it and all problems went away.

Bill

[Daz(DJLFlapper)]

One thing that gave me a problem was that the con rod to piston was slightly oval on the crank shaft. this little rod caused the engine to resonate and vibrate when running. Yours could be the same unless you know different. Sorry cant think of anything else.

I have just bought a raptor 30 with the 39 ringed engine. In the instructions it says to make sure what fuel I use. Any idea what I should use.

Pete

20/20 combo is good ..stay off the 15 percent nitro..it will make the engine run hot..If you can get a nitro at 30% your better off .it will make your engine run cooler