I have a Murray Riding Lawn mower with a 12.5 hp Briggs and Stratton engine with a NIKKI carburetor. I was asked by my son to try to fix it for his Friends mother. I have rebuilt the carburetor, changed the spark plug, changed the oil and fuel filter and fuel It starts but will not run it kills it's self, I was wondering if anyone out there could help me?

Mark Starr
Life Member 
mlstarr68@bellsouth.net  

It could be anything that will interfere with gas or air. Air cleaner, gas cap vent, choke, old gas line,{ cracked or sucking air},or even the grounding cable. Maybe it set for a long time and has varnish in gas system. That is all I can think of off the top of my head. Main thing is , check out gas and air supply start to finish. Best wishes

Mark,

It really sounds like a fuel problem. You said that you rebuilt the carb. that 'should' have taken care of that if the problem was there.

Did you also replace the fuel line? or lines? Does it have a primer bulb to pump? if it does there is a fuel line in the tank that quite often gets eaten away by the gas.

Also look for a fuel filter IN the gas tank, at the end of the fuel line. You should be able to snag the line with a hooked wire to pull the filter out.

If you would post all of the numbers off the engine, series etc. then some of the experts could steer you better.

Let us know.

Bob........54646 Central Wisconsin's most fun guy! Handy member since 3/14/'94

Just had the same problem with my Murray.   Found sediment in the fuel tak, even though I replaced the old gas.  Also blew out the filter & fuel lines. Works okay now, but I need to get a new fuel filter just because.

get the round car type that you can see in  its far better then the briggs filters   cost about 3 bucks

Harry G.Frederick

Mark, have you adjusted the carb since the re-build? Initial turns outward on the screw
adjustment 1&1/2 to 2 turns should get you running enough to make final adjustment.
Also, you said it "kills itself"....are you on the tractor when this happens  or standing beside it?
If the latter .... the problem could be a safety related switch at the clutch/ brake pedal or kill switch under the seat. You said that you replaced the fuel filter....did you check to see if it is directional
or not ( with an arrow indicating direction of flow)? If installed the wrong way ....it could restrict the gas flow to the engine. Just my thoughts...hope this helps.........jheffner