21 hp briggs motor probs


Old 04-08-07, 05:30 PM
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Join Date: Apr 2007
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Exclamation 21 hp briggs motor probs

I have a 21 hp briggs mower and i have cleaned the carb replaced the gas new plugs new filters new gas line everything i could think of i am pretty skilled with motors cars mowers ect ....... now i am stumped ok heres the problem when the mower is running without the blades engaged it pops like water in the gas or poor fire but thats been eliminated , when under a load mowing no popping just governs up and down i have also checked the shear key to make sure the timing is correct , also the valves are clean and gap is good , i am truly stumped on this one the mower is only about 4 years old with only about 75 hours on it any help would be great thanks,,
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Old 04-08-07, 06:46 PM
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Location: canada
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You say it's "popping" at a fast idle with no load & the govenor is "hunting" when the blades are engaged & the engine is under load?? It sounds like it's running lean. You said you rebuilt the carb, have you tried to adjust it to fix this condition??
Old 04-09-07, 05:14 AM
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Location: Upstate New York
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I agree with hopkinsr2 inthat it will be a carburetor issue. But this engine likely has no adjustments, other than idle speed. What you need to have a close look at is the main jet and i'll bet that there is a minor restriction in such. You may well be able to clean it out with torch tip cleaners but if you post back with the model, type and code numbers I can provide you with the part number for a new jet, which would be the best way out as they are relatively inexpensive to purchase.
Old 04-16-07, 03:25 PM
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ok here is what i have its a 21 hp briggs and model is 407777 do u need #s off of the carb to thanks, Dave
Old 04-16-07, 08:29 PM
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I agree, the carb needs a cleaning at the least. I've had the same problem on those engines and a good cleaning does the trick.

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