Throttle control problem
I am breaking in two RCGF 20cc gas engines in my Great Planes Revolver for a Kemp 95" B25. I just changed engines after 52 flights on my first engine. The second engine runs fine as did the first. The only difference I find is the RPM does not change much until I am below 1/4 throttle. I believe the only difference in the set up of the two engines may be the engine throttle arms. I have the throttle linkage on the outer hole of the servo arm with the end point adjustments down to 25% in each direction. Should I move the the linkage to the inner hole of the servo arm and increase the servo end points? I have not had this problem with the other 5 gas engines I have used. Any suggestion on how to make the throole more lineor would be appeciated. Thanks P51TOM