Lawnboy won't quit running

Easy48827 · Aug 3, 2017

I have a 2 cycle 6.5 hp Dura Force Lawnboy which is a real work horse. Today I mowed and when done the kill switch did not work. No problem- I'll pull off the spark plug wire but it kept running with no spark! These things have a large gas tank so no time to wait 1/2 hour to run out of gas so I am thinking how I can get it to stall. I go to turn in the needle screw on the side of the carb and it finally stopped on its own. Can these diesel without spark? I am running 45-1 synthetic 2 cycle oil I use in my boat motor. I also tuned the adjustment screw until I thought it sounded right. What can cause this and how can I prevent it in the future? TIA!

flyerdan · Aug 3, 2017

It sounds like there might be a bit of carbon on the head, or plug (or perhaps the wrong heat range plug) that is acting like a hot spot allowing it to run like a glow engine. That's all that I can think of given the circumstances; chances are your kill switch is fine. If you don't want to tear it down, maybe source an old inner tube to run over and stall it when you're finished, save messing up the carb settings.

Easy48827 · Aug 3, 2017

Never replaced the plug so I'll do that first. Also, it doesn't look like too much trouble to pull the head and clean the carbon. Any idea the torque on the head bolts?

flyerdan · Aug 3, 2017

Looks like 140-200 in. lbs. I'd download the whole manual here.

Easy48827 · Aug 3, 2017

Got it! Thanks very much!!!

4get gto · Aug 6, 2017

How did you ever make out with this?. I'm kinda curious how long it would have run with the spark plug off.

coolreinfarm · Aug 6, 2017

The boat motor oil is for water cooled engines, the mower is air cooled and you need to use oil for air cooled motors, this will reduce carbon buildup on the head. I bet the combustion chamber was glowing when you pulled the plug wire off and that kept it running.

Easy48827 · Aug 6, 2017

Actually I am using Golden Spectro motorcycle oil in everything 2cycle I own including boats, dirt bikes, outboards, and weedwackers, etc. A friend owns a Honda dealership who races and he advised me to do it 20 years ago. Never had a problem. This Lawnboy was purchased used and I had to rebuild the carb to get it going. I was thinking more the way I tuned it was the issue. I haven't gotten to pulling the head yet. I have another project I'm working on I have to get done first.