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Little help needed troubleshooting LX277 Engine Misfiring

3341 Views 9 Replies 6 Participants Last post by  Justy37
I have an LX277aws with the FH500V 2-cyl engine. I've already syphoned out the old gas and replaced with fresh 93 octane. The fuel filter is new, the air filter is new, the carb has been inspected and cleaned. The spark plugs have been replaced and gapped to .040 per JD spec. The engine seems to idle ok but as the RPM increase there is misfiring. Could a coil be going bad causing the higher RPM misfire? I've already pulled each plug individually while it's running to see if it dies, and each cylinder is firing as the engine stays running. Any suggestions to narrow this down without throwing parts at it?
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Any feedback would be appreciated! I bought a new coil and tried swapping each coil with the new one but it still runs the same. I also did a valve job and made sure they were set to .006 in.
Is a valve sticking? Sometimes when you have a engine with a lot of hours. The valve springs, loose there spring and are weak. So at higher rpms, they can not function fast enough. Lot of high horse power engines have bigger stronger springs that can push the valves back faster and keep up.
How would I determine if this is the cause? There is no hour meter so I'm not positive on that.
Is there a spec in the JD book for spring psi @ installed spring height?
That is how it is done on car/truck motors.
Dave ----
Certainly not in the owners manual. Possibly the tech manual, which I dont have. Anyone else have any suggestions?
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