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Briggs & Stratton mower won't run, smokey exhaust

SteveR's Avatar

Join Date: May 2006
Posts: 5

08-26-06, 09:00 AM   #1  
Briggs & Stratton mower won't run, smokey exhaust

I've got a John Deere push mower with a 6.5hp Intek OHV engine that I bought last spring used for $75. It has been smoking since I bought it...it blows out puffs of blue smoke, not consistently, but sometimes it will make pretty thick puffs. A few weeks ago it just quit on me & wouldn't restart. I pulled the carb apart, cleaned it, and it ran again for about 30 minutes and quit again. Pulled the plug, it was coated in oil, cleaned it, lowered the gap, and it started right up. The plug had a faily heavy crust on it from the burning oil. The smoke and oil covered plug make me thing the rings must be shot. Ran for another 30 minutes after lowering the plug gap and then it died again. I cleaned the carb again using a different carb cleaner, but now can't even get it to cough, even with starting fluid. I do get a good spark on the plug when I pull it and crank the engine, so it must be fuel or air, or the rings are shot so the compression is too low and it need a rebuild (or replacement).

Because of the smoke and oil coated plug, I'm leaning towards just buying a new mower. I don't feel like spending half my day trying to troubleshoot this thing, I've got too many things to get done. I don't mind doing anything myself and have done nearly a complete rebuild on a small block chevy, but don't feel like wasting my time on a $75 lawnmower. Are there any easy checks I can do on this thing, or should I just go buy a new mower? Does the smoke & oil on the plug likely indicated bad rings or a worn cylinder?

Oil is at the full line, and it is a float-type carb.

I pulled the valve cover, both rocker arms have about 1/8" of slop, i.e., the rocker arm is loose enough that when I move it to the valve, there is about an 1/8" gap at the pushrod. What is the torque spec for the rocker arms on these engines? Should it be that loose? I've never seen an automotive engine that didn't keep some pressure on the pushrod and valve spring at all times.

I checked the flywheel shear key, it is perfectly aligned, so there shouldn't be any spark timing problems.

Last edited by SteveR; 08-26-06 at 10:35 AM.
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puey61's Avatar

Join Date: Apr 2004
Posts: 3,224

08-26-06, 10:58 AM   #2  
What weight oil is in it? It must be SAE 30W if conventional, petrolium based oil, and either 10W or 5W 30 if you use a synthetic oil. Is the mower on a level surface when you check the oil level? Rather critical, but shouldn't be related to your trouble, is the spark plug gap. The 12 cubic inch Briggs need the plug gapped at .020". The valve clearances will be .004-.008", provided you have a 12 C.I. engine. Rocker arm torque will be 100 inch lbs. Rocker cover torque is 45 inch lbs., again provided it is a 12 C.I. Do the valve guides seem tight? Perhaps oil seeping past the guides, if not a piston ring issue that is? Post back with the engine ID numbers!

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