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Posted by David Sherman [72.47.9.228] on Thursday, February 24, 2011 at 11:10:43 :
In Reply to: Re: O/T snow blower engine help needed posted by Ron in Indiana [71.97.178.223] on Thursday, February 24, 2011 at 08:20:05 :
If it's like most small engines, the governor is a pretty crude affair consisting of some bent sheet metal, wire, and a light spring. The behavior you're describing is called "hunting" and is a risk in any governor system. I could get technical about it and write out the equations, but the gist of it is that there are three parameters that ought to be controlled in an ideal governor system, most systems only attempt to control two of them, and only one (the basic speed) is controlled by the obvious adjustment screw. My light-duty portable generator also hunts at no load, but stabilizes when any load is applied, so I haven't tried to fix it.
If you want to try to fix it, look at the governor mechanism, see that there's some kind of screw to adjust the basic speed, and then look for a place where some part of the linkage or a spring is attached to one of several holes in a lever or arm of some sort. By moving the attachment to one of the other holes, you can change the "gain" of the system and make it stop hunting. Hunting is basically due to too much gain and the motor not being able to respond as fast as the governor can move. When the motor is lightly loaded, it can respond faster to governor position changes, which makes it more likely to hunt. A better system would include a dashpot to slow down the movement. With less gain, the actual speed will vary more as the load changes, but that's not as big a deal on a snow blower as it is on a generator.
Anyway, look at the linkage and see if there's a place with several holes and some spring or wire you can hook into any one of those holes, and try moving it to a different hole.
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