I have a JD 425, 20 hp gasoline engine. I can mow for about 10-20 minutes, then the engine will being to choke out. If I cut off PTO and throddle back, it will smooth out. I can let it sit for awhile and it will do the same thing again. Later, I may mow for hours without a problem, but it always happens when within 10-20 minutes when I first start it up in the day.

I have changed all filters, blown the fuel line, pull gas tank to make sure no debris, changes plugs, cleaned carb and tried a new coil on each cylinder (2 cylinder with coil on each). I'm baffled as well as JD service department.

Respectfully, does anyone have any ideas what could be the problem? The money is going to add up as I try to replace parts.

Thank you

Check the fuel pump pressure with a tee in the line so U can see if U are getting the correct preeeurs U must use the tee because the pump is vac driven and need the load on the mower when U check I usuall put a 3' hose on and tape the gauge to the hood when checking the pressure when the mower is working hard acrack in the vac line to the fuel pump can cause lots of problems


Mike

I like Mikie's answer, and it may show the problem for you. Not being too familiar with a 425, I don't know how the fuel tank is vented, but if it's possible to loosen the cap as soon as the engine starts to miss, you could find out if the vent system is working.
If you are in the habit of filling the tank each time before you start, it would probably take that long to form a vacuum in the tank. Then stopping for a while could let it relieve the vacuum. After using a certain amount of fuel, it would take longer to draw that much vacuum again.
Just a guess, and you may have already checked this out. Hope you find the problem!

tommyhawk

Doug425,

I am not familiar with a 425 but same sort of thing used to happen on my fathers 110 and it was always the points & condenser. Change them out and it ran perfect again. Does the 425 have points & condenser?

SamV

the crank case is vented right into the inside of the air filter, the dirtier the filter, the more it sucks oil, when its not fully warmed up the plugs cant burn the oil, cause its a liquid cooled kawasaki, Two Banger!!!!!!!


You might think im CRAZY, cause you dont think yours is using any oil, but it dont take much , when it isnt warmed up!

I have a little over 700 hrs on my 425, and it likes to stumble untill it decides its warm enough to saw the grass!!!!!!!!!!!!!!!!!!!! and in the stumbling process it likes to puff black smoke rings!!!!!!