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I've been working on a 2004 Lawn Boy 10323 that doesn't have any power. It's my father's and I'm trying to fix it for him. He told me that last year it started losing power and was hard to start. This year, it had no spark so I changed the coil. It started right up but wouldn't run right. The carb was dirty so I cleaned it and added a fuel filter. I put in a fresh NGK BMR4A, fresh fuel with Lawn Boy oil mixed at 32:1, cleaned the air filter and made sure the choke wasn't stuck and the governor was working properly. When I removed the cover over the exhaust transfer pipe, raw fuel came out. I replaced the needle and seat and set the float to 1/2" as I read on this site. The exhaust port was clean but the muffler was a little dirty. I cleaned it up, reassembled everything and it starts up but after a couple of minutes, it loses power and doesn't want to run. The only thing I can guess is wrong is the reed is bad. It doesn't surge or act like it has an air leak. Apparently, from looking at the short block exploded view from Lawn Boy, you have to split the engine cases to replace the reed. What else could it be?
 

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Sounds like you've done everything right. I would suggest checking the oil seals, especially the top one. I've seen them pop out. Another thing I would do, is look very carefully to make sure there isn't an obstruction in the fuel line or even in the fuel tank somewhere. In fact I would start there. It sounds to me like it might be starved for gas. Double check your float setting, too - make sure it's not upside down.

I had an older Lawnboy act like this, and I found grass caught in the fuel shutoff.
 

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Lawnboy Green
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From your description, my guess is seals. If the carb is clean with a good air filter and so on. The float is set correctly and not flooding, the engine has clean exhaust ports, then its getting some air through those old seals. This outside air is leaning out the fresh fuel charge to the point where its not producing any power. Would seem to happen as it warms up? Check the cylinder compression psi with a gauge if one is available to see where things are at. Seal quality took a nose dive when Toro took over Lawnboy. Original Lawnboy seals have springs inside them that hold the seal to the crank, these last. The newer seals are super soft and have no springs thus they wear quicker and become brittle from the heat.

Put the mower up on its side and take a close look at the crank where it exits out of the crankcase right above the muffler plate to see if its leaking a little oil and looks wet. You will need to remove the engine from the deck and open the case enough to pull out the old seals. I use either Permatex Ultra Black rtv or spray copper on the case halves. Drive in the new seals with a big socket or a piece of pipe untill they are just flush with the casting. Not too deep. Use a piece of sandpaper to clean up the crank on the bottom and oil the crank when your sliding the new lower seal on.

The reed valve is a one way trap door that allows the crankcase to be filled with fuel and air mixture called charge. As the piston starts its downward stroke, charge pressure in the crankcase starts to build. The reed valve or trapdoor is closed by this pressure. After a few more degrees of crank rotation, the transfer ports open and the charge is pumped up around the piston to the combustion chamber. Ive seen bad reeds that have had pin holes in them from rust. Ive also seen a few missing reeds, ones that were pumped right on through the engine. Check the reed when you have the case halves apart to replace the seals. Chances are the engine would not run at all if the reed was broken.

If you have questions, please post them.

Best wishes,
Bob
 

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LAWN-BOY-AHOLIC
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Seals most likely, is there an oily area around the lower crankshaft? If so the seal is leaking, the top seal could be leaking or popped out also. I would also check that the carb mounting screws are not too tight, it doesn't take much torque and too much could warp the plastic carb flange and create a air leak. You will find it, good luck!
 

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Discussion Starter #5
From your description, my guess is seals. If the carb is clean with a good air filter and so on. The float is set correctly and not flooding, the engine has clean exhaust ports, then its getting some air through those old seals. This outside air is leaning out the fresh fuel charge to the point where its not producing any power. Would seem to happen as it warms up? Check the cylinder compression psi with a gauge if one is available to see where things are at. Seal quality took a nose dive when Toro took over Lawnboy. Original Lawnboy seals have springs inside them that hold the seal to the crank, these last. The newer seals are super soft and have no springs thus they wear quicker and become brittle from the heat.

Put the mower up on its side and take a close look at the crank where it exits out of the crankcase right above the muffler plate to see if its leaking a little oil and looks wet. You will need to remove the engine from the deck and open the case enough to pull out the old seals. I use either Permatex Ultra Black rtv or spray copper on the case halves. Drive in the new seals with a big socket or a piece of pipe untill they are just flush with the casting. Not too deep. Use a piece of sandpaper to clean up the crank on the bottom and oil the crank when your sliding the new lower seal on.

The reed valve is a one way trap door that allows the crankcase to be filled with fuel and air mixture called charge. As the piston starts its downward stroke, charge pressure in the crankcase starts to build. The reed valve or trapdoor is closed by this pressure. After a few more degrees of crank rotation, the transfer ports open and the charge is pumped up around the piston to the combustion chamber. Ive seen bad reeds that have had pin holes in them from rust. Ive also seen a few missing reeds, ones that were pumped right on through the engine. Check the reed when you have the case halves apart to replace the seals. Chances are the engine would not run at all if the reed was broken.

If you have questions, please post them.

Best wishes,
Bob
It looks oily around the lower seal area. It appears you have to pull the flywheel (with a puller tool?) to get to the top seal. If I'm going in, I'm replacing the reeds regardless of how they look. Once I pull the flywheel and remove the six bolts holding the cases together, it there anything else to remove to get it apart (other than the carb)? I see two retaining rings on the bottom end, one above and one below the seal, in the exploded view. Does the lower one come off before splitting the case or does it just need removed to get the seal off? Then, do I reassemble the case and drive in both seals? Thanks for your advice up to this point, I'm sure I'll have more questions.
 
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