Craftsman riding lawnmower odd problem

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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 blades off.
Any advice on what is the problem and how I address it?
Thanks!
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Did you give up the idea of bolting a motor to your bicycle and try to use the lawnmower instead to go to work?
Nick
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stryped wrote:

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 flywheel effect.
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 throttle settings.
Martin
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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.
Pete Stanaitis ------------------
Martin wrote:

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Can you tell me where the govenor is on this engine and what it looks like? This is a Koler engine. spaco wrote:

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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.
Pete Stanaitis --------------------
stryped wrote:

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have you ever changed the air filter?
http://www.minibite.com/america/malone.htm
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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 shaft!
Paul
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stryped wrote:

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.
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I dont let it sit dry. By the way, I always leave the throttle in the fast position and it still does it even if I move the throttle to slow. Stubby wrote:

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previous post.Some carbs have an "air bleed screw" that can be adjusted to alleviate surging sometimes.Drop the bowl on the carb and clean it also.
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stryped wrote:

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 erratically.
Stuart
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