Bill,

You're lucky the engine hasn't died in the air yet. I had a G26 on the same plane, ran great on the ground, would die in the air or on landing or just not put out power. After reading in the gas forum, I installed a brass fitting on the metering diaphragm cover and ran a piece of tygon tubing inside the fuselage. Problem solved. What is happening is varying air pressure is acting on the metering diaphragm affecting the air fuel mixture while the plane is in the air. With the tubing running inside the fuselage, that pressure variation is minimized. The carb on the G26 is a tad bit big so it makes tuning very touchy.

I wrote this in a thread in the Gas Forum sometime back regarding the same issue on a G26:

"4. Next and most important, assuming your mixture screws are facing down toward the ground which is the common installation. In this position, the fuel metering diaphragm is facing into the prop wash, ie forward. The variable atmospheric pressure from the prop and air stream effects the performance greatly by my experience. The engine runs fine on the ground, but sucks when it's airborne. Then you begin to chase your tail to adjust the carb to no avail. My G26 was initially installed on an Ultra Stick Lite with the engine exposed like on your plane. I had a least a dozen dead sticks and a crappy running engine until I took the advice to solder a fitting on the metering diaphragm cover in order to run a vent line into the fuselage and to plug the exist hole with silicone. Engine now ran sweet on the ground and great in the air, day and night difference, no more dead sticks. Well the plane ultimately crashed and the engine is now on a profile plane with the engine fully exposed again. Since it was a profile, I didn't run the vent line into the fuselage, just ran it back under the fuselage. You guessed right, the sweet running engine now didn't run worth a darn. Two of the first three flights were deadsticks. The vent line is now inside the fuselage, engine runs great and no more deadsticks."

Good luck and let us know how it goes.

Chuck