I have a 5 or so year old craftsman riding lawn mower 48 inch cut. It
seems to run fine while mowing if th eblades are engaged. However, when
I turn the blades off after mowing for awhile, the engine surges like
someone is making the throttle go up and down. It "jerks" while you are
tryign to drive it. I can remember if it still surges when in neutral
or not but it is bothersome when you have to drive somewhere with the
Any advice on what is the problem and how I address it?
It sounds as if the governor may be "hunting" under light load due to
slight misadjustment. I'd check to see if the spring or other parts of
the linkage may be damaged or binding. Engaging the blades could
smooth this out by either adding load, which would possibly cause the
throttle governor to move to a less-binding position, or by their
I guess it's also possible that the low-speed carburetion circuit may
have a problem, causing the engine to govern poorly at nearly-closed
I agree that the problem is most likely with the governor. There may be
a build up of crud somewhere in the system that makes the governor bind.
this would be particularly true if the governor uses a vane in the
flywheel's air stream to sense the engine speed.
Since it's a Kohler, it probably has an internal governor which is not
likely to get full of grass clippings. Later posts may be more to the
point for you, but I would be surprised if the carb's throttle shaft of
bearing surface wears that badly in only 5 years unless youb put Lots of
hours on it.
I have had several of that type mower and all suffer from the problem
you describe. The problem is the throttle shaft wears the pot metal
carburetor housing until there is quite an air leak around the shaft.
The excess air makes the engine run lean and slow down until the
governor recognizes the slow-down and gives it a shot of fuel. The
whole cycle begins again.
Only solution is a new carb. Not worth the effort to try to fix it.
Usually there are other pieces getting ready to fail, such as the
spring on the governor rod or the throttle arm falling off the throttle
I'll bet you run it dry when you put it up for the winter. That lets
the diaphragm in the carburetor get hard. It can't flex right and the
accelerator pump won't work right. Get a rebuild kit, throw away all
the replacement valves and nozzles, just install the gasket/diaphragm.
It takes about a half hour.
On some tractors, when the blades are off, there is a brake pad that
Scuffs the top of one quill to stop the blade rotation, and lifting the
blades to the off position should also move the deck forward to slack
the drive belt. If the belt is not going slack, or slack enough, the
motor may be trying to turn the blades against the brake pad and running
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