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briggs & stratton 15.5 hp OHV backfires through carburetor

Posted by vandredi 
briggs & stratton 15.5 hp OHV backfires through carburetor
August 21, 2011 09:29PM
i have a craftsman lawn tractor with a B&S 15.5 hp OHV engine, engine model=28N707..type=0173-01.. it had been setting for several years due to a coil problem, i repaired the problem a few weeks ago, the kill wire had grounded out killing the fire, so i put it on a toggle switch, the mower will crank and run, no problem, but it popps or backfires thru the carb, you can see fire in the carb, i have tried many things to correct the problem to no avail, here is what i have tried, 1;checked the key way=no shear..2;changed the spark plug= no change..3;gaped the coil at .010=no change..4;removed and cleaned out gas tank=no change..5';replaced fuel line and filter=no change...6; cleaned out carburetor with a guitar string and cleaner, all ports clear, solenoid working correctly= no change...7; removed head and inspected,& lapped the valves cleaned off carbon deposits, replaced head gasket ,push rods are fine...8; put head back on & adjusted valve lash to (in) .004...(ex) .006 = still popping, i also checked all gaskets to intake and carb,..it will smooth out at one place on the throttle, almost full throttle, but if you try to idle it down any the popping starts, the choke is working properly and all linkage is correct, i checked it with images from the B&S web site, this thing has me stumped, i dont want to use it backfiring like it is, and im sure it must be fixable, the mower has had light use over the years and is in great condition with no alterations other than the kill wire is now on a toggle switch, if any more information is needed please ask, i tried to be as detailed as possible in my description...thanks for your time

Edited 1 time(s). Last edit at 08/21/2011 09:30PM by vandredi.
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