11HP B & S engine backfires through carb.


Old 08-22-08, 11:33 AM
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11HP B & S engine backfires through carb.

I have a problem on a riding mower with a 11hp B&S engine. It was running fine then just died as if it was shut off.
When I try to start it now, it actually backfires through the carburator. The mower is getting spark and fuel. I checked all the basic stuff and even replaced the plug, float and needle valve. Results are the same, while it is cranking it backfires through the carb.
It even caught fire once when it backfired.. Any suggestions?

Last edited by evetheodis; 08-22-08 at 11:34 AM. Reason: more info added
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Old 08-22-08, 12:37 PM
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Maybe pull the head off and see if a valve seat popped out of place.
Old 08-22-08, 04:45 PM
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Post your engine model, type and code numbers please.

How is the oil level in the engine?

Was the fuel you were using fresh?

There could be a problem with a sticking intake valve, or valve seat as CPeppy advised.
Old 08-22-08, 05:31 PM
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Or that some tiny eyeglass sized throttle plate screw did not vibrate out and fall into the intake port, and is either lodged between valve and seat, holding the valve slightly open, or is floating around in there, and may even be hiding in there one minute and lodging the next.
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