FT-160 Twin in Vario Boxer Heli
I have a Vario Boxer helicopter with an OS FT-160 twin. I am extremely experienced with helis, but this FT-160 has me puzzled. I have it running and flying and it produces good power, however, when off idle the left cylinder smokes less than the right cylinder. I have been checking both cylinder head and exhaust pipe temps and the temps are even between the cylinders. (180-190 degrees F). I am not dropping a cylinder in flight because the heli can't maintain flight with one cylinder down.
Some important details, I am in Colorado, at 5000' msl and the average temps are n the md 90's. I am running cool power 15% heli fuel and OS Type F plugs. I have McDaniel's glow driver on it set to come on below 1/3 stick. The engine is mounted vertically with the prop end (and carb) below the cylinders. The motor is cooled by a fan mounted on the crank drawing air down over the motor. Each exhaust has it's own tuned pipe and there is a pressure tap from each pipe to the fuel tank, so it is pressure feed to the carb. It is the old air bleed carb. The engine is very low time, I got it from a friend who passed away a few years ago and he had never finished it.
I checked the valve lash, all the valves were at .006" to .0075" lash, I reset them all to .003". I also checked all tubing and exhaust piping and didn't find anything.
The engine is running well and the heli is flying well, I have tried richening up the mixture up to where I could not lift off and really did not see a difference. I have tried different fuels and have not made a difference. Does anyone have any ideas what to check?
Thanks!