misfires under load

clintmn

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Just bought a well used Snapper with Kubota WG740 gas engine. It has 1700 hrs, plus some severely deferred maintenance. It starts right up and runs well, although it produces a heavy cloud of oil smoke until it warms up. My problem is that as soon as the governor opens the throttle up under load, it starts to miss and load up, black exhaust smoke.until the deck clears out. Previous owner replaced coil, cap and rotor. It seems that the spark is breaking down under load. I tried closing down the plug gap, but that didn't help. Compression is 150 on all 3 cyl.s. Air filter is not plugged. Looks like #3 is my smoker, swapped plugs around, no change. Seems to miss on all cyls, so I tried a dfferent coil wire. no help.???????????
 

jp1961

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Hmmm,,,that's a ton of hours. Try a hotter spark plug maybe?

Regards

Jeff
 

dfbroxy

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It sounds to me like the previous owner may have tried to run diesel in it. Let the engine warm up untill it starts to act up and shut down. Then use a little gas in carb to try to restart. If this works its diesel. Remove fuel tank and fuel lines empty and clean.
Remove carb bowl and clean. Then reinstall. Warm engine up again, if it stalls then keep it running with squirts of gas in carb again. This time continue to keep engine running. This could take up to 30 min.... All the diesel in fuel system is very resistant to come out. The diesel didnt harm the engine so dont throw parts at it untill your sure this is not the case.
 

clintmn

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Hmmm,,,that's a ton of hours.

Regards

Jeff

Yep, but a well cared for liquid cooled gas engine could easily last twice that long. Unfortunately, this one was not! When I bought it, there was no oil showing on the dipstick, and no coolant in the radiator. Belonged to an OTR trucker who left its care to his kid.
 
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