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88' 318 governor surges with Onan

Phil My 318 blows snow great no problems except for some small back-fires at low RPM. In the summer cutting gas it runs fine for the first 15-20 min than it begins to surge with the governor. When cutting at full throttle the governor opens further to higher RPMs for 3-4 seconds than back down and will continue till you shut it down so it can cool off. I have blown out the motor so it doesnt have any junk in the cooling fins. It does seem like it does run hot. Could it be running rich, a carb problem or the valves need adjusting? Any help thanks Phil
Dave Phil - Usually if an air-cooled engine is running hot, the carb is adjusted too lean. But if your governor linkage is out of adjustment, that can cause engine overheating.

Here's some things that can cause surging:

choke cable out of adjustment
governor linkage needs adjustment
carburetor could be out of adjustment
fuel filter could be clogged
fuel pump could be weak
valve clearance could be off

Tony Bachler Interesting I took my 318 out of storage Started mowing, It surged not much enough to be annoying, After checking the price of a new mower my mind was made up.New oil/filter Air/fuel filter. Checked the linkage, no loose or broken mice homes.I took off the air cleaner housing, top of the carb. after inspection of any dirt particals in the bowl; took some paper towels dabbed the gas out sprayed the carb. with carb cleaner. cleaned it all out. Put it back togather again. It runs better then new,. OH A word of caution. DON"T TAKE ANY LINKAGE OFF AND REPOSITION IT.THAT WILL CHANGE THE RPM.AND THE HARMONICS OF THE ENGINE, IT WILL SELF DISTRUCT IT'S SELF. That engine is designed to turn at a spicific rpm. no more no less. At full throttle.
Bill I have a 1987 318 with a p218 engine that has a similar problem. The engine has about 1100 hours on it and it burns a bit of oil. It runs great for the first 20-30 minutes and then the RPM's increase and stay increased until I idle it down. If I stop and let it idle for a few minutes, until it cools down, it does not rev as high until I mow for a few minutes again. It appears that if I idle it down, after it has been mowing and has reved up, to the RPM sound it had before it reved up it does not burn as much or any oil. Iíve had the air cleaner, plugs, oil, oil filter, and fuel filter replaced this past spring when I bought it and it still did it. I also checked the fins on the sides of the motor and they are all clear and free of grass.

I brought it to a mechanic and he said the governor was going out on it and it was not worth fixing. He said the governor was the first thing into the engine and the last thing out and I would be better off just replacing the engine. Does anybody know if this is true and if not how difficult is it to replace the governor? Or does anybody have any suggestions as to what the problem may be?

Thanks for the help.

joe carpenter I have the same problem as Bill. After about 30 min the engine speeds up, but can be idled down. Does anyone know problem and how do you adjust gov.

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