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I had the exact same mower, same model number, and.....same problem. Drove me nuts, tried checking everything, replaced the coil, check compression, etc. Pulling the plug help cool it back down quicker. Cold no problem, hot forget it. I resorted to using a Velcro strap on the handle to keep the mower running anytime I needed to stop. Not the safest, but at least I was mulching. After a few seasons and my son getting old enough to help, I sold it and got a Honda. I do miss that LB. Wish they still sold the two strokes.
 

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Discussion Starter #22
JAF1
I got one I can sell ya.
Your post is funny. That is exactly where I am. Kind of had enough of trying to figure out this no start hot. I think I will just leave the squeeze clamp on it that I have been using for testing and be done with it.

***Thanks to everybody for your interest, tips and suggestions.
 

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I worked at lawn mower shop in decades past[ dont ask when, but it was before the 90's; If a lawn boy came in with a no start condition hot or cold and has spark, it needs both top and bottom crank seals. compression will be fine but sucking air and mixture is to lean to start and run. thats why the one respondent when he sprayed fuel into spark plug hole wold start once it got spinning fast enough it would pull in a richer mixture and keep running
 

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Discussion Starter #24
One time during testing got it hot, shut if off, got a no start, so I pulled the spark plug and shot some starting fluid in, reinstalled the plug and nothing. Priming and the choke also had no joy.

BTW this model was built in 2000
 

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Discussion Starter #25
Change of heart. After sleeping on it I have decided to replace the upper and lower seals on advice of others.
And the fact that I am bull headed. Just can't quit until I get her done.
I just ordered parts. Updates to follow.
I also know if this works it not only helps me it may help others with there machines.
 

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Change of heart. After sleeping on it I have decided to replace the upper and lower seals on advice of others.
And the fact that I am bull headed. Just can't quit until I get her done.
I just ordered parts. Updates to follow.
I also know if this works it not only helps me it may help others with there machines.
You have a very frustrating and unusual problem, so here are a couple of weird things to look at when replacing the seals. You have stated numerous times when hot you have no spark or possibly intermittent weak spark. I would try the following possibly before replacing the seals. You have tried 4 CD coils and same result, so it's safe to assume they are not at fault. From your posts, I think you have eliminated switches and external wires grounding by removing at the coil. But what about the flywheel and flywheel key? Very uncommon on Lawn Boys but happens frequently on Broggs engines. A dented or cracked flywheel key or hairline crack in the keyway can cause all kinds of weird ignition problems including opening the ground path when the parts heat up. It spunds like you have lots of LB parts. Try a different flywheel and key. Spark plug as well. Hope you solve this.
 

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Discussion Starter #27
I have checked the key ( was fine ) and also swapped flywheels with a used one from my used parts inventory. No change. Has new spark plug in it.
 

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Wow, that's a really tough one. Sorry for the bad spelling above as well. I guess you can't edit once posted on here. I hope the seals solve the issue.
 

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While you are in there replacing seals don't forget to look really good at the crankcase for leaks that could be manifested when the cast aluminum is hot. The case halves need to be sealed good, also I have heard of pin holes developing in cast aluminum crankcases over the years that could be the source of the problem when hot (on a D series LB a few years ago). Who knows, a previous owner may have split the crankcase and didn't clean the old sealant well when he/she reassembled, or maybe one of the case halves is slightly warped and not sealing good enough when the metal is under thermal expansion. The reason I harp on this is you have done a good job of ruling out everything else that in my mind a crankcase leak almost has to be the culprit.
 
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