flying a Modified Quick pro60 that has been converted to a zenoah 23 power, flys good, but the tail jerks sometimes. Im using a 2.4 radio system, all seems smooth on the bird.

Not sure if it effects the 2.4 systems, but it might be your spark plug. Alot of us that run modified 260s in our gas boats use a NGK CMR7H (3066) without any problems.

Belt tension?

tail setup?

Gyro?

is it hunting or wagging? does it do it more in one phase of flight then the other?

Any vibrations?

motor broken in well?

You need to further define the problem.

it seems smooth, the tail is jerky, every now and then , just jerking around, no rhym or reason, not horrible, i still can fly it, just makes me wonder, the motor sounds smooth.

something doesn't sound right. From my experience, if the tail is bouncing around it could be a few things. Gyro could be picking up some noise from somewhere, bad bearing, tail belt improperly adjusted, wires routed close to some source of interference etc.

Definitely check your mixture. If you get out of the proper range, the engine doesn't run as smooth as it should and it can definitely cause the tail to kick. I had mine start doing it just before it blew the glo plug out of the head. Gas and nitro aren't the exact same animal so I wouldn't expect everything to be the same but I'd look at vibration issues/bearings/engine problems first if all else looks good

thanks ill double check all

check your tail section as sometimes the set-screws come loose on the shaft and it will slip when under a load and be fine at times this condition will get worst if left unchecked also if your tail has a long control rod that are 2 pieces (like the raptor) where the 2 rods come together there is a connector check that as they come loose at times also

thanks alot