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FT-160 Twin in Vario Boxer Heli

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Old 07-24-2011, 04:04 PM
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DStJohn
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Default 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!
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Old 07-25-2011, 06:04 AM
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Bax
 
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Default RE: FT-160 Twin in Vario Boxer Heli

With the twin-cylinder engines, one cylinder will ALWAYS be leaner than the other. You just have to set the engine so that the leaner cylinder is not running too lean, and let the other one take care of itself. It's a fact that multi-cylinder engines will not get even fuel distribution unless you have direct fuel injection to each cylinder. Full-size aircraft will show the different cylinders with different exhaust gas temperatures when normally-aspirated. That shows an uneven distribution, and you lean the engine to the cylinder that runs the hottest...same with model engines.
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