I think John hit it on the head there. My ARF trainer was flying just as you descrive, a slight change in throttle would result in huge pitch differences. At the last, I had a stack of four popsicle sticks under the TE of the wing and it was flying much better.

I also had a 4*60 that I broke the tail off of and when I repaired it, I screwed up the horziontal stab inicidence just a bit. I had to fly with a bit of down elevator trim, but this was sensitive to throtle.

I would get an incidence gage, or rig one up and see where you stand. I'll bet the wing is off a bit, probably to much incidence. You have a low wing, so if you were to put one popsicle stick between the wing and fuselage at the TE, your problem should be a little worse if the incidence is the cause.

One other possibility is motor down thrust, You could always add a washer or two on the top two screws on the motor mount to give a little more down thrust.


Don

Don