I have a older Brison with electronic advance with polished case and it has always run great.
The problem is at idle there is no happy medium as far as a slow idle to a "little faster" idle.
I know all about how to set the transmitter to work a gas carb but even working by hand it can go from a nice slow idle and then move the arm a little....a little more.....a hair more....then like 500RPM more all at once.
Jim

Look at the linkage geometry between the carb and throttle servo. Sounds like everything might be set up "equal-equal" with a throttle rod that is too long.

Inside hole at the throttle servo, as far out as you can go at the carb lever, with linkage length determined when both the servo and carb arms were at their halfway points.

Ok, Your reply told me that I might not have a problem with my gas carbburetor which I wasn't sure about..... and to look at my linkage setup.
You might be right as I have taken off a ZDZ 40 where the servo is hooked directly to the throttle arm and mounting on my Brison 2.4 where as you know has this nice linkage to move the throttle arm. The geometry has changed.

I will get the plane out of the trailer today and also look at my computer transmitter and see if I have the throws set to a 100%.
Thanks
Jim

Proabably no problem with the carb itself. Incorrect linkage lengths and positioning cause a lot of problems with throttle resolution, which your issue sounds to be. Small movements making big changes falls into that category.

Any one here know Milton In SC or GA, he does engine work.  I need to get his address and phone#

http://rcextremepower.net/

Auburn, Ga's best