Did you clean the screen on the back of the inlet adapter? I've seen much younger ones plug solid (not pass 60 psi air). When almost plugged it will sure starve an engine.Could it be that the drain plug sticks into the float chamber enough to hold the float up so it can't drop and open the needle valve all the way and so restricts fuel for full throttle running? Most carburetors have two mixture adjustments, idle and power and for the intermediate range the only adjustment is a finesse of the float level. Seems like that might be possible. Has it carbon or copper wires? Magnetos are especially critical to needing copper or iron wires, no carbon wires? Do the plugs have resistors, same problem? It may be simply that the no load adjustment for the high speed jet is a bit on the lean side and for power it needs to be opened up a bit. Then it will run a bit rich no load at speed and may even soot up the stack, but it shouldn't be so rich as to foul plugs or put out visible black smoke. I know my MF-135 pulls the plow best when full rich. Gerald J.
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