By Rusty Beavers
I'm working on a Coleman UTV 400 that has a rough idle, owner has had it for about a year. When I say it has a rough idle, it doesn't have the continuous smooth running sound. At times you can hear it kinda skip, sputter, or like the RPM has fallen (RPM stay constant according to the gauge) It's not as bad as it was after I replaced the fuel filter and fuel injector (both are Chiki) not sure if that is a quality brand at this point. Checked the spark plug, it was a little foul, but not too bad. (Since the engine is still idling bad I'm going to replace that) Cleaned the throttle body making sure the carbon and soot has been removed, and the air-filter has been cleaned. New fuel is being used so it's not old or been standing. They did tell me that they were using non-ethanol fuel, not sure if that would be causing the issue. Next two things I can think of that maybe the issue is the O2 sensor or the valves need adjusting.
Thoughts and suggestions? Thanks in advance.
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?
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Time for the 200 hour service. I did see that someone finally put a youtube video up. Only thing it is missing is the spark arrester service. Anyone know anything about that? I did see a youtube video, not related to this one, for doing that service but it is very suspect. I'm not a fan of beating on parts with a rubber mallet.
Anyway, here is the video that I will using to do my service. Hope it is of use to some of you.