B&S won't die - keeps running


Old 05-08-09, 10:46 AM
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Join Date: May 2009
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B&S won't die - keeps running

After about 1&1/5 hours mowing the lawn I let go of the safety-shutdown lever and it kept running. It ran rough, smoked, backfired often, but kept chugging along. I backed the throttle to slow but it kept chugging. Next I pulled the sparkplug wire. More smoke, more backfiring, rougher running, but it kept chugging. Then I headed to an unmowed field in a park. It kept chugging and cutting grass. I pushed it into thicker and more overgrown grass; it kept chugging and cutting the grass. Next I pushed it into some really tall weeds that I would not have attempted if it was running normally. Finally it stalled. Beer 4U2

I realize that it was dieseling. Was any damage likely done while it was running like this? What could be causing this? Possibly a partially sheared flywheel key? Or the flywheel brake needs replacing?

A little background: This is a 6.5 hp Briggs & Stratton Intek Edge OHV engine, manufactured in Feb of '99. Model 121682; Type 0122 E1.

It usually starts with one pull, however this time it would start but die after a few seconds. Short blasts of starting fluid kept it running until it warmed up and then ran as normal.

After a couple minutes of mowing I ran over a piece of plastic drain pipe and stalled the engine. It restarted on the first pull and cut the rest of the lawn with no problem, no roughness, no vibration. No turning it off when I was finished either!

Is it worth it to buy a flywheel holder & puller to check the key? Or should I take it straight to a shop? Or is this engine so near the end of its normal operating life that the less spent the better?

On a related note do all these Intek engines leak oil from the OHV cover like sieves?

Confused in Lexington, KY

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Old 05-08-09, 12:11 PM
Join Date: May 2006
Location: Iowa!!!!!
Posts: 3,728
Dieseling like that can be caused by carbon in the cylinder. It gets hot while running and serves to ignite the fuel. That can be cleaned out with additives or take off the head and clean it manually.

Also on a hot engine if the throttle isn't closing altogether you can get dieseling.

If the mower started right back up after hitting the tubing, I doubt if you sheared the flywheel key although advanced timing will contribute to dieseling.

If by chance the key was sheared by a sudden stop at the load end of the engine, the flywheel will normally move to advance the timing.
Old 05-08-09, 10:04 PM
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You can observe the flywheel key condition just by removing the flywheel nut. If the keyway on the shaft and the keyway on the flywheel are not perfectly aligned, it is sheared.

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