2011 Craftsman 21hp 540cc Platinum XRD Briggs and Stratton OHV engine / Backfire

LLB Tractor-SC

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  • / 2011 Craftsman 21hp 540cc Platinum XRD Briggs and Stratton OHV engine / Backfire
Engine has been bullet proof / trouble-free up to now. Sudden loss of power; engine constantly backfiring through carburetor; over-rich exhaust with gas smell. Engine was running fine when this problem occurred. Changed spark plug; no help. Removed air filter, started engine. Constant loud rapid backfiring through carburetor; very loud.
Mower is Craftsman 42" cut model 917.289223. Engine family: 9BSXS.5402VB (Dec 2009 date of mfg). Researching carburetor solenoid as possible problem. Mower out of operation. Any ideas?
 

bertsmobile1

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  • / 2011 Craftsman 21hp 540cc Platinum XRD Briggs and Stratton OHV engine / Backfire
First thoughts is a stuck float flooding the engine.
This requires disassembly of the carburettor and a thorough cleaning.

Second thought is a fractured flywheel key.
Cheap & easy to check, pull the cover off and the flywheel retainer there shoud be two rectangular slots, joining together to make a perfect square.
 

Scottrw

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  • / 2011 Craftsman 21hp 540cc Platinum XRD Briggs and Stratton OHV engine / Backfire
Engine has been bullet proof / trouble-free up to now. Sudden loss of power; engine constantly backfiring through carburetor; over-rich exhaust with gas smell. Engine was running fine when this problem occurred. Changed spark plug; no help. Removed air filter, started engine. Constant loud rapid backfiring through carburetor; very loud.
Mower is Craftsman 42" cut model 917.289223. Engine family: 9BSXS.5402VB (Dec 2009 date of mfg). Researching carburetor solenoid as possible problem. Mower out of operation. Any ideas?

I am having the same problem and was curious what you found to be the problem? Thanks!
 

Tinkerer200

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  • / 2011 Craftsman 21hp 540cc Platinum XRD Briggs and Stratton OHV engine / Backfire
Remove the valve covers and check push rods.

Walt Conner
 
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