Since I've seen some questions on this I took some pictures and will provide instructions on a valve adjustment for the UT400. This should be the same for the 550's and other various Coleman/Hisun single cylinder models with the cylinder slanted aft.
I have seen several people ask of it is really necessary, and read several reports of valves being out of adjustment from the factory. My valves were .004" intake, and .010" exhaust with about 5 hrs on the machine. I've seen different numbers thrown around for factory spec, but I decided to go with 0.005".
This is called valve lash. What is is is a gap between the rocker arm and the valve then the camshaft isnt opening the valve. Why does it matter? If it's too large the valve doesn't open all the way, if it's too small the valve dosent close. This can cause valve damage (overheating) as well as loss of engine power (burned fuel is going out exhaust rather than pushing the piston dow).
Tools required : 5MM Allen wrench, 10MM box wrench, needle nose pliers, flat feeler gauge set, rags
First you need to remove the fan cover on the passenger side. There is a cooling vent hose on the back side, remove the hose clamp and slide it off. From there there are 4x 10mm bolts holding the cover. The forward ones can be accessed from under the seat.
Next remove the spark plug from the drivers side. Carefully wiggle the spark plug wire off. Grip it as low as possible and give it a little twisting motion as you pull it off to help free it. Its a tight fit for a socket, but there is a sheet metal wrench in the toolkit that fits it. Unscrew the plug and set it aside. This allows you to spin the motor over freely with no compression to fight. When you reassemble this is a good opportunity to switch to an NGK iridium plug for better performance/less fouling DR8EIX)
Next you need to remove the intake and exhaust valve covers. The intake us the forward one. There are 3x 5MM Allen screws to remove. The Exhaust is the rear with 2x 5MM Allen bolts. Both covers have O-Rings instead of gaskets and are reusable. When you remove the rear be careful and use your rags as there will be oil that drips out.
Next up we need to spin the motor over to top dead center. Grab each rocker arm and give em a little wiggle up and down. Spin the engine over by grabbing the fan with your other hand. Spin the engine over until both rockers have some wiggle and are loose.
Once both rockers are loose slide the feeler gauge in like shown above. Try different feelers as needed to determine your starting spec. You should feel some drag but still be able to move the feeler without too much force.
If you need to adjust, use the 10MM wrench to slightly loosen the locknut, then with the correct feeler gauge in place, tighten the top square nut while wiggling the feeler in and out. Once you have it right you need to tighten the 10mm lock nut without moving the square head bolt. Once the lock nut is tight recheck the clearance.
That's it, button everything back up and make sure you have it all reassembled before running it again.
If you find this helpful give me a thumbs up or comment. If you have any questions or need more help let me know. If there's interest maybe I'll do some more of these
Hopefully this helps somebody because I couldn't find any info on this runaway condition.
Drove 1/2 mile to the gas station and when I started up to leave the starter stuck on. Turn key off starter is still running~! Limp it home wondering what the heck to do, get it in the garage and pull the negative battery terminal to get it to stop. Whew, WTF?
Calm down and start checking things, starter is hot of course but nothing is smoking and nothing smells burnt. Pull battery cover off and start checking wires from battery to relay and relay to the starter. OK good nothing is hot, nothing is crispy and nothing is melted. Probably smoked the starter though. If this had happened to my wife and I wasn't around the machine would have run until the battery died and probably melted down/burned.
I'll get to the point to save you folks some time and trouble. Because this is a kymco machine you need 2 different Kawasaki parts to make this repair, and information is scarce to say the least. The switch and a sub harness to connect it to the machine's plug.
Everything works now, but the starter sounds horrible so I'll be changing that too before spring.
Good luck out there and hopefully this is just a freak occurrence, but if I were you I'd get rid of this kymco part and put the Kawasaki replacement in now.
Switch, Magnetic is part number 27010-0767
Sub Harness Start Relay is part number 26031-Y034
Recently acquired a 21 year old Mule. The previous owner let the brake master cylinder run dry, and when I flushed the brakes, one wheel's brakes locked up. I took the wheel off, but cannot get the axle nut off, and there is not enough space to get my gear puller behind the drum anyway. Anybody had an issue with seized brakes? How can I get this thing off to replace it or rebuild it?
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?
By Nate ward
Having issues with the IR model 421275 transmission. In 2wd it takes playing with the throttle to get it to engage in fwd or reverse, if you flip into 4wd, it goes into gear perfectly. Once moving, you can go back into 2wd and everything works until you stop. I changed hyd fluid and have ran the linkage in and out. Any thought on the issue?