That 30mm carb is too big for that engine. This is why you are showing lean with 140 jet. Your engine is like a vacuum. With the proper carb and jetting the volume of air being sucked through carb creates a negative pressure thus sucking the fuel up through the main jet. The 26mm carb with correct size jet will provide the engine with proper fuel at higher rpm. Compare what you have to a vacuum. You have a 5 HP shop vac with a 1 1/2" diameter hose and it will suck up a 3/4" x 2" bolt no problem but put a 3" hose on that vacuum and it won't suck up a 1/2" diameter rock. Go back to the stock carb and properly jetted you will have more power.
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