By
Werhat
Hi folks,
I have a Mule 550 (FE290D engine) that sat for several years and would not start. A few years ago I replaced the fuel filter and carburetor, at which point it started right up and developed full power. More recently, I've changed the air filter, fuel pump, ignition coil (gapped to spec), and spark plug, and adjusted the valves. The engine still has a lope/surge at part throttle and at idle. Rather than idling at a stable speed, it speeds up and slows down until it quits. It snaps to life right away if I open the throttle, so I don't think it's starved of fuel. I can always get it to restart immediately if I choke it while cranking, then it will die after several seconds again. It takes some cranking to start hot when not choked. I've tried adjusting the idle mixture, but no setting seems to make it stable. It won't idle at all with the throttle fully closed; I have to turn the stop screw to hold it slightly open.
I suspect it's getting idle air, since the passages are open, but that the idle jet isn't providing adequate fuel, such that I am having to hold the throttle open and idle it off the main jet which isn't stable. This is just speculation. I've cleaned the idle jet and tried a larger size, but it made zero difference. The carburetor seems to be clean. It's been doing this since I installed the new carb. The gas tank seems to be clean, although it's hard to see inside.
I posted a video of what it's doing:
What's next? Try another carburetor?
Thanks.
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