Replacing the coil in the right magneto and carefully re-timing both mags. seems to have solved my ignition problem. I ran the motor and taxied around the airport for a few minutes. At 1700 RPM I have a 100 RPM drop on the left mag. and less than that on the right. Everything seems to be back to the way it was before all this.
Well not quite everything, now the motor hesitates and sputters when you try to accelerate from below 1000 RPM.
If it had an automobile carburetor I would say the accelerator pump is bad. Opening the throttle allows more air through the carburetor. At the same time that causes a slight increase in pressure in the throat of the carburetor, of if you like, less vacuum. This means there is less pressure differential to push the fuel from the float bowl into the throat. Both changes, more air and less fuel, mean a leaner mixture, which, depending on the mixture just before the throttle is moved, can cause the motor to misfire or lack the power to accelerate. On an automotive carburetor they solve this with a little accelerator pump which squirts just a bit more fuel into the throat to richen the mixture. It works, in my '63 Corvette you could slam your foot to the floor and the car would still accelerate without hesitation, while smoking the tires and slamming you in the seat.
On airplanes we generally avoid jamming the throttle open quickly. Also, no one wants the motor to sputter when you're trying to recover from a bad landing and need full throttle, now.
It's possible I've got a small air leak between the carburetor and the cylinders or some dirt in the carburetor after setting 26 years. I won't know until I get things apart. I've ordered a carburetor kit from Fresno Air Parts. It's coming by 2 day Priority Mail which means it should be here in the next 2 weeks, oh well. It's already 2 days and the tracking just says it's In-Transit. I'll get back on it after Christmas.
Merry Christmas!
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