while my Honda PC-50 was sitting for a month after my friend crashed it, we switched the carburetor with the one from my friend's newly acquired pc-50. So I know this engine runs with a good carburetor on it. It seems to choke out as soon as the rpm's get up into the cruising range (with or without load). Originally we thought it was the seal between the main jet ,basically an O-ring, causing extra fuel to flow past the jet. We fixed that with another O-ring, then we tried epoxying the jet to the carb to be absolutely sure it was sealing, and no difference. I just found out the only way i can make it go is to remove the whole cap and slider assembly from the carburetor. It goes like crazy with the throttle removed, faster than it ever went before, but i have to control it by covering the hole where the slider goes with my thumb. It's like an on/off switch like this, it's either to the floor or idle, and there is a delay when i put my thumb on the whole before it starts slowing down.