# Old B&S 3.5 HP running rich, sputtering



## oldbriggs (Sep 20, 2004)

Engine model 92902, Type 1796-01
"Pulsa-Jet" carb-I think. Has 2 pick up tubes; 5 screws hold carb to tank.
OK I know I should just replace this 24 year old mower (Murray, aluminum so not rusted out), but it seems like it should be an easy fix.
Started running rough, sputtering like a fouled plug or dirty air filter. GRADUALLY got worse over 3 or four uses. Adjusting needle valve leaner helped a little. Eventually had valve turned all the way in- still running if tank is near full. Replaced plug (very black- too rich, like it sounded. New filter. Got a carb rebuild kit- new diaphragm/spring, needle and seat, etc. Everything looks great and clean. Squirted carb cleaner everywhere.
Where is the sneak path for fuel? Runs exactly the same with new parts. Still runs with needle valve all the way in. Plug gets sooty black quickly. 
What am I missing? Choke is not stuck closed...

Bruce


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## bugman (Aug 12, 2004)

try a autolite plug, spraying the carb down with cleaner while running, clean combustion chamber and make sure the oil is clean and a little below the full level. if that don't work i had one around 30 some years old, got a peice of crap newer one to get the new style tank and carb and put it on and ran great.


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## snoman (Feb 13, 2004)

oldbriggs
There is also one other thing you can look at. On some of the older Briggs models, the carb/tank mounting seems to have a tendancy to warp. Briggs has a .002 shim that goes under the carb right in the middle. You might want to try that.
One other thing to think about is have you lapped the valves and are they in spec?

snoman


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## oldbriggs (Sep 20, 2004)

Thanks for the great tips. I'll have another go at it before giving up. I'll keep it even if I do break down and get a replacement, just so I can fix it for a spare when I'm not under the gun to get the yard mowed. It's rained a lot here in NC and the yard needs some attention.


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