LB 10550 No Start When Hot

14 years ago

When cold 2 pumps on the primer, choke on, starts 1st pull every time. Runs great when cutting. I can't tell you when this symptom started because I have always used a battery clamp to keep the engine running until I was finished cutting. Last week I decided to bag clippings and shut off the mower to empty the bag, then I discovered the problem.

I must have pulled with no results 10 times with the throttle on fast. Next step was prime a few times and choke on but no luck with that. Then pulled the plug which looked dry, dipped the plug in gas, reinstalled and started right away without lots of smoke. All of this was repeated twice over until I finished the yard so I don't think it is a fluke.

I don't have the time right now to tear into it but I did glance at the lower shaft and did NOT see oil so I think that rules out a lower shaft seal leak.

I have no idea what could be causing a fuel delivery fault with these symptoms. The only other idea I have is that it could be the coil getting weak and my messing around with other things gives the coil time to cool down.

I have 2 other DF's I can swap parts with but would like some opinions before I dive in.

Thanks.

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Comments (7)

romore_gw
14 years ago
Remove the muffler and check the piston for scoring.
1saxman
14 years ago
I think you answered the question when you 'primed' the spark plug and it started. It's not getting sufficient fuel on a hot start. Why? Good question, but these mowers are starting to get old, and it probably could use a carb rebuild, or al least a good cleaning.
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weed_cutter
Original Author
14 years ago
Thanks for the replys. I did drop the "U" tube and checked out the piston and exhaust. All clean and OK. I think I'm going to swap a coil from another mower and see what that does. I don't want to get stuck in a loop but I have changed coils on these things more often than the plugs.
evdpgh
14 years ago
This seems a lot my Lawnboy 10420 problem. A good strong dose of Seafoam seemed to solve my problem. Worth a try anyway for the cost involved.
weed_cutter
Original Author
14 years ago
Just a quick update. Carb cleaning didn't make a difference, it's not the coil either. I have found that if I choke the engine to stop it restart is not a problem. Really strange because I'm sure it's not running lean.
1saxman
14 years ago
'Rich' can cover up many problems. Amateur mechanics find that they can make engines run by throwing more fuel at the problem. OTOH, 2-cycles do like their fuel.
Let's think about what's going on in the engine; you've been using it and it's hot - you stop the engine and the fuel in it evaporates to some extent. If you use the choke while it's coasting down, it sucks in extra fuel, so there's some in the crankcase for re-starting.
But it didn't always do this, so something has changed. I wonder if it actually is running lean because of a pressure leak in the reed valve. This would blow some fuel back through the carb. In this scenario, you probably would have a gassy air filter.
weed_cutter
Original Author
14 years ago
Thanks for the idea, I'll be checking for that next week. The only other idea I've had is that it might be overheating. I'm going to be looking at the cyl fins at the same time.