Surging problem

Smitty154

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Currently working on a Craftsman LT 1000 with B+S OHV 16. Cannot get this motor to run smooth. I have replaced the Carb, fuel lines, filter, flushed tank , adjusted governor and even checked flywheel key. If I push up partially on to choke is the only time it will smooth out. The bowl solenoid is functioning and fuel is flowing well to the carb, any suggestions?????
 

cruzenmike

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Carburetor jet o-ring! Had a similar problem with my Briggs engine and this fixed my problem. Ethanol in the fuel takes a toll on the rubber components in the fuel system. The o-ring will shrink allowing fuel to get past the jet and the increase in fuel will make the engine surge. I replaced the o-rings along with doing a carb rebuild kit and did the governor adjustments and problem solved. If this doesn't fix your issue, your governor gear may be on its way out. I also had to replace one of these on the same engine 20 hours after my carb rebuild.
 

Smitty154

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Carburetor jet o-ring! Had a similar problem with my Briggs engine and this fixed my problem. Ethanol in the fuel takes a toll on the rubber components in the fuel system. The o-ring will shrink allowing fuel to get past the jet and the increase in fuel will make the engine surge. I replaced the o-rings along with doing a carb rebuild kit and did the governor adjustments and problem solved. If this doesn't fix your issue, your governor gear may be on its way out. I also had to replace one of these on the same engine 20 hours after my carb rebuild.

It's a new carburetor! I have a kit coming for the old one so I'll soak that for a few days and rebuild the old one. With the ability to smooth out on choke the governor appears to be working ok.
 

cruzenmike

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It's a new carburetor! I have a kit coming for the old one so I'll soak that for a few days and rebuild the old one. With the ability to smooth out on choke the governor appears to be working ok.

If you are having to smooth out on choke, is it possible that there is some other issue with air/fuel, possibly the fuel pump, filter or air cleaner assembly?
 

bertsmobile1

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Start the engine then when it is warmed say a minute or so manually move the governor to allow the engine to increase speed.
Do it fairly slowly and don't hold it flat out just one smooth run up to fully open and back down.
IF you have a helper, get them to sit in the seat and turn the blades on because just like your car, it is not good to race a mower engine without any load on it.

The instant the engine stops spinning remove the dip stick

If smoke comes out you head gasket is leaking & requires replacement.
If the engine accelerates smoothly then you have a problem with the governor

If the engine splutters & misses then you have a problem with your fuel supply , spark plug or module.

Try a new plug and CHECK THE GAP they are not necessarily correct right put of the box.
Put an inline red neon tube spark tester on the engine.

Run the engine as before with blades engaged but hold the throttle slightly faster than the high idle for a minute or so while watching the spark tester.
If the tube flickers in time with the engine missing then it is the module / plug/ plug cap or kill wire ( or kill switch )

Eliminate the kill circuit by repeating with the kill wire disconnected.

If the spark tester glows solid during the stutter try spraying some WD 40 FROM A TRIGGER PACK all around the carb & manifold when running fast.
If engine changes speed then you have an air leak.
 

cpurvis

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Surging can be the result of the mixture being too lean. If it has an adjustable main jet, try opening it up a little and see if that helps.

It may also be a leaky gasket on the intake.
 
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