Lawn Boy 10323 Dies After 10 Minutes and Cannot Pull Starter Cord

[mikulskn]

My lawn boy 10323 mower will run for 10 minutes and then slowly die. At that moment in time, I cannot pull the cord. But if I remove the spark plug, I can pull the cord again.

- I have cleaned the carb and jets, including idle jet a few times.

- Installed new spark plug.

- Installed new ignition coil.

- Removed exhaust plate underneath and took off exhaust pipe transfer and that looks clean.

- Cleaned filter.

- Put new governor spring on.

I originally thought it was a fuel problem, so that is why I cleaned the carb a few times. That carb never looked dirty, and I cleaned everything really well. And given that the mower will run for 10 minutes from cold, I dont think it is fuel.

I changed the ignition coil and spark plug to eliminate that.

I noticed every time after it died that I could not pull coil. I could pull it again after it cooled down. So then the next time it died, and when I could pull starter cord, I tried removing the spark plug right after it died, and then I could pull the starter coil easily. I thought it might be vapor lock, but there is no extra fuel in the cylinder and the spark plug is dry.

I am thinking it is valves or exhaust. But inspecting the exhaust transfer pipe underneath showed the transfer pipe to be clean.

Any advice on what to try next? Thanks!

 

[dcgrazier]

My thought is worn bearings on the crankshaft. You will need to tear the engine down to verify. I had an F engine that exhibited similar symptoms. It finally seized. Someone had used the mower and either straight gassed it or more likely did not properly mix the gas and oil.

 

[mikulskn]

Thanks for the thought on maybe worn bearings on the crankshaft. I guess it probably isn't worth my trouble. Could it be valves of some sort?

 

[Phototone]

Thanks for the thought on maybe worn bearings on the crankshaft. I guess it probably isn't worth my trouble. Could it be valves of some sort?

Your LawnBoy 2-stroke engine does NOT HAVE VALVES in the sense that 4-cycle engines do. The Piston acts as a valve, along with the reeds in the reed plate behind the carb. The reeds generally are foolproof unless they rust, and if they were rusted you couldn't get it started in the first place. If the engine seizes up after it gets warm this tells me you are mis-fueling it. Stop! Use ONLY ethanol-free gasoline, whatever grade you can get, even Premium is good, as long as it is ethanol-free. Use 4 oz of 2-cycle oil (I use LawnBoy brand) per gallon of fuel. Mix well in the fuel can. Add a dollop of Marvel Mystery Oil to the mix for extra goodness. Your lawnboy has roller bearings on all rotating parts, they generally don't seize up. No, I think it is the piston, and I think you are mis-fueling it. Your DuraForce LawnBoy engine is jetted very lean. In the context of 2-cycle engines that means it operates on the verge of too little oil and gas (because they are mixed together), and in my opinion ethanol-enriched fuels kill 2-cycle engines.

 

[mikulskn]

Thanks Phototone for the nice write-up. I have been using ethanol based gas in the lawn boy for years with no problem. So are you saying that as the mower as aged, it is probably lacking good lubrication at this stage in its life? And therefore, switching to non-ethanol fuel and good 2-cycle only, that this might give it better lubrication? Are you thinking the rings on the cylinder wall get to tight as it heats up, and the lack of lubrication won't allow it to get moving freely (and then stall)?

 

[bertsmobile1]

Ethanol adsorbs water from the air plus overnight condensation.
It is fine in your car that you use all the time but not in a mower.
The water / ethanol mix enters the engine as droplets which burn & turn into steam inside your engine much the same as water injection that was used to boost the power of bombers to get them off the decks of carriers in WWII
However the steam scours the bore, stripping some of the oil from the surface ( steam cleaning ).
Add to this that the water / ethanol mix, does not carry any oil with it into the cylinder so you are a tiny ( and I mean tiny) bit short on oil for every cycle to start with.
On top of this the idiot lean burn legislation means the engine is right on the border line of insufficient oil and too lean so you are getting conditions of both overheating and lack of enough lubrication then add is the scouring of the water and you engine is in trouble.

The net result looks the same as running strait gas only not quite as drastic.

 

[lewb]

My lawn boy 10323 mower will run for 10 minutes and then slowly die. At that moment in time, I cannot pull the cord. But if I remove the spark plug, I can pull the cord again.

- I have cleaned the carb and jets, including idle jet a few times.

- Installed new spark plug.

- Installed new ignition coil.

- Removed exhaust plate underneath and took off exhaust pipe transfer and that looks clean.

- Cleaned filter.

- Put new governor spring on.

I originally thought it was a fuel problem, so that is why I cleaned the carb a few times. That carb never looked dirty, and I cleaned everything really well. And given that the mower will run for 10 minutes from cold, I dont think it is fuel.

I changed the ignition coil and spark plug to eliminate that.

I noticed every time after it died that I could not pull coil. I could pull it again after it cooled down. So then the next time it died, and when I could pull starter cord, I tried removing the spark plug right after it died, and then I could pull the starter coil easily. I thought it might be vapor lock, but there is no extra fuel in the cylinder and the spark plug is dry.

I am thinking it is valves or exhaust. But inspecting the exhaust transfer pipe underneath showed the transfer pipe to be clean.

Any advice on what to try next? Thanks!

If you scored the piston and cylinder wall the only fix is to replace piston and attempt to clean up cylinder wall. I was out of country and my son fill up a 4.75 lb with gas he thought had oil in it. Took about 15 minutes to seize up. Let cool would run again. The heat took out the cdi. When I got home I replaced the cdi and went to mow lawn (had oil in gas) ran for about 10 minutes then seized again. I just found a used mower to replace it. My guess you need to take motor apart and inspect. Piston is easy to replace, getting cylinder back in shape is not especially if you do not have the tools and experience. You can get a short block (cylinder, crank and piston)for 100.00 or so, you just need to take parts off your existing LB and transfer to the short block. Actually pretty easy to do with basic tool, will need a torque wrench. There are a few you tube videos on doing this as well.

 

[Phototone]

Depending on how bad your engine internals have been damaged, I suggest the following possible treatment. (This is considering you have run ethanol-enriched fuel and 50:1 gas/oil ratio up to now)
1. Get some (for sure) pure gas (no ethanol) Any grade will do, regular unleaded or premium, just no ethanol.
2. Make up a 16:1 gas/oil ratio mix. (1 gallon gas, 8 oz 2-cycle oil)
3. Drain your existing fuel from the fuel tank, and refill with this mix.
4. Squirt a little Marvel Mystery Oil into the spark-plug hole and turn over engine (without starting a few times to distribute the oil)
5. Start and run engine and see how it goes. (It will smoke while it burns off the Marvel Mystery Oil) and it make smoke a bit anyway with a richer oil/gas mix.

Report back to us.

If it stays running with the richer mix of 16:1 Gas/oil, then after you use up the gallon, you can try the recommended 32:1 gas/oil mix...just NO ETHANOL. While it is true that modern 2-cycle oils "may" provide greater lubrication than older oils would...you have to remember that your DuraForce engine is jetted too lean just to meet EPA regulations of the time, so it really isn't getting enough oil to begin with.

 

[EdBrown]

I am not an experience small engine mechanic, but this happened to me.

I once put on an ignition coil, and had the correct space between the coil and the flywheel magnet. However, apparently my screws must have slipped a little, or maybe I didnt have them quite tight enough. Put all back together, and pull cord would NOT pull at all. Puzzled for awhile, but took the shroud off again, and the coil was up against the flywheel magnet, with no space in between. I reinstalled the coil, and made sure the spacing was right, and that the screws were TIGHT. No more problem, pull cord worked fine, started quickly. This is just a thought.

 

[fabricgator]

If you scored the piston and cylinder wall the only fix is to replace piston and attempt to clean up cylinder wall. I was out of country and my son fill up a 4.75 lb with gas he thought had oil in it. Took about 15 minutes to seize up. Let cool would run again. The heat took out the cdi. When I got home I replaced the cdi and went to mow lawn (had oil in gas) ran for about 10 minutes then seized again. I just found a used mower to replace it. My guess you need to take motor apart and inspect. Piston is easy to replace, getting cylinder back in shape is not especially if you do not have the tools and experience. You can get a short block (cylinder, crank and piston)for 100.00 or so, you just need to take parts off your existing LB and transfer to the short block. Actually pretty easy to do with basic tool, will need a torque wrench. There are a few you tube videos on doing this as well.

lewb,
Where would one go to purchase a short block for a hundred? This is already made up with the bearings and all?
Thanks.