Looks like you may have found to quickest easiest way to add weight to the crank on a PT to fix this kickback problem.
I'm just thinking if the kick back problem could be solved by slowing down the speed at which the decompressor shuts off.
If you put a large hose in the middle of the decompressor hose would that slow down the time it takes to shut off the decomp giving the engine a better momentum to fire without kickback.
Experimenting will soon tell you if the larger hose works better or a small jet in the decomp hose is better to slow down the time it takes to shut the decompressor.
Another alternative is a larger spring in the decomp may help ,just thinking of all the old chainsaws that the cord rips out of your hand when starting if you forget to turn on the decomp.
I know how bad the PT will kick back without the blade plate but with the PT Pro 460 engine with no blade plate I never got any kickback when starting and that has only a slightly heavier boss on the crank and no restrictor in the decomp hose.
Possibly if you could change the speed at which the decomp activated, this may mean the extra weight on the crank wouldn't be needed.
I think I remember you tried a restrictor in the decomp before but just wondered if a larger pipe would work better, like a couple inches of 3/8 hose or 4 inches of 1/2 inch hose.
