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I just recently purchased a 10323 Model Lawnboy self propelled mower. It has a Duraforce 6.5 HP motor silver series and runs great. I recently cleaned the carb, replaced the float valve and seat, cleaned the air filter and put fresh gas in the mower. I am running a 32:1 gas mixture. The mower runs great, but then randomly will quit. Usually after a few minutes of use. When it stops if I prime the mower 3 times it will start right back up and run great. There is no surging or irratic behavior just the random shut off.

Could this be a coil problem or an issue with the carb itself?

I think there is an adjustment screw on the carb, call it an atmospheric valve or something, allows regulated air into the float bowl. Weird deal but usual adjustment is about 2 turns open. Does nothing to actually adjust the mixture. Might solve the problem if not a coil going bad.

tom3 said:

I think there is an adjustment screw on the carb, call it an atmospheric valve or something, allows regulated air into the float bowl. Weird deal but usual adjustment is about 2 turns open. Does nothing to actually adjust the mixture. Might solve the problem if not a coil going bad.

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There is a screw in jet on the side of the car under a sticker. I took this out and cleaned out the passage as well as the jet itself. It looked to flow pretty well. Unfortantely I still have this issue. The mower always starts right back up. I did look at the fuel line right after it shut off. It looked like fuel was refilling the carb. I do have to re-prime 3 times and it will fire right back up. I ran it for almost 10 minutes with no issue. Idle speed is solid with no surging at all.

Could my float itself be bad? I have read sometimes they swell just slightly and stick against the carb body. The float does float fine in gasoline as I tested that a week ago.

Loosen the gas cap a little and see if it stays running. May have a plugged vent in the cap.

Rivets said:

Loosen the gas cap a little and see if it stays running. May have a plugged vent in the cap.

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This was my first thought. So far I appears to flow without an issue. I took apart the gas cap and make sure it was not plugged up.

Did you try running it with the cap off or very loose? Did you try starting immediately after it stopped, cap off, no prime? Are you sure nothing is blocking the tank outlet? Sounds like something is stopping the fuel flow. If nothing changes when you do these three tests you will have to pull the carb and check your float needle and seat. Also, double check the model number you posted. In my searching it does not come back with a Duraforce series.

Does this carb have a rubber seat for the float needle? Might double check and make sure it's all the way in place.

Rivets said:

Did you try running it with the cap off or very loose? Did you try starting immediately after it stopped, cap off, no prime? Are you sure nothing is blocking the tank outlet? Sounds like something is stopping the fuel flow. If nothing changes when you do these three tests you will have to pull the carb and check your float needle and seat. Also, double check the model number you posted. In my searching it does not come back with a Duraforce series.

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Here are some pictures of the mower.

tom3 said:

Does this carb have a rubber seat for the float needle? Might double check and make sure it's all the way in place.

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From the factory it does have a needle with a rubber tip. I have since replaced that needle and seat. The float has been tested in a cup of gasoline and floats without an issue.

Parts Replaced:
-Float needle/seat (FLOAT IS ORIGINAL)
-Spark Plug
-Fuel line with a new filter
-Carb disassembled and cleaned thoroghly (Jets removed soaked in carb cleaner)
-Jet on the side of the carb cleaned (Screwed back snug)
-New float bowl gasket
-New intake gaskets
-Gas Cap taken apart and cleaned

When the mower shuts off it must be primed 3 times before it will restart. If this was a coil it wouldn't restart until cold, this mower starts up after being primed.

How long can the mower run with fuel in just the float bowl? Should the jet on the side of the carb be screwed out 2 turns as mentioned earlier? A service manual would be helpful too.

Just an FYI, I'm famaliar with 2 strokes as I ride 2 stroke street bikes. RZ350, Yamaha Enduros.

Hello,

It's possible the coil is bad,,,I have a 10323 Duraforce that doesn't start, but if I leave it in the sun for a few hours to warm up, it will start.

Check the grounding wire to see if it's shorting out anywhere.

Regards

Jeff

I have fixed this issue. My previous parts list is above, but the only item I didn't replace was the float itself. When I tested the float to see if it would float in a cup of gas it passed without an issue. After some extensive research it appears these floats can swell. This causes the float itself to stick against the carb body. I replaced this float with a new OEM piece and my mower ran for over 30 minutes without an issue. I ran it through wet grass, tall grass, nothing could stop it.

I LOVE THIS MOWER.

Good to see you got it fixed. Have to file this away for the future myself. These mowers/motors do seem to run better when loaded up.