Hi fellows. I have an OS 91 FX mounted on a Great Planes Big Stick 60. I broke the motor in on a stand and put it on the plane today. I am using a 14X8 prop. At Idle the plane viberates very bad. Enough that the main landing gear jumps all over the place. When you throttle up it seems to get better and not viberate so much. I have balanced the prop and rechecked it again and again and still the same thing. Any suggestions will be greatly appreciated. Thanks and keep on flying.

Although you've balanced the prop have you tried changing it out with another say perhaps a 13X8, it could be possible that the hub may be out of balance.

could be drilled off center too, or you are too rich on the low end and it is detonating and not running smooth

Hey

If it's not your propeller then I would look for your idle adjustements, normally it is the little screw in your throttle arm on the engine... The engine can also be too rich so it is not running smooth or your gas is not good! Hope this will help...

Thanks

Hey fellows thanks for all the suggestions and help. I guess it is all a learning experience. One of the guys from the club came by and asked me to show him how I hab balanced my prop. Well guess what? I was doing it all wrong. He first balanced the hub and then the baldes and it ran as smooth as silk. Once again thanks for all the help and fly them till they drop.