Engine Surge / Stall on John Deere EZTrak z445

Old 08-24-11, 11:16 AM
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Engine Surge / Stall on John Deere EZTrak z445

Hello and thanks in advance to anyone who can help me.

We purchased a new John Deere EZTrak Z445 zero-turn mower in 2009...it has the 25hp Kawasaki V-Twin engine. I performed the yearly maintenance with the kit from the Deere store earlier this year (oil, filters, plugs); it has just over 60 hours on it now.

A couple weeks ago, I noticed the mower throttle surging up and down during operation, but it stopped after a few moments. I was almost finished with the yard, and I didn't think too much about it. The next week when I mowed, it started surging again and then the engine began bogging down in heavier grass...this is odd because NOTHING bogs this mower down. Right after that, the engine died. I let it cool for a moment and started it back up. For a few minutes it ran okay then it started dying on me again. Each time I would have to choke it to re-start it. When I would engage the blades it would go dead...I kept re-starting and finally it started going dead even before I would engage the blades. I put the mower up and finished the yard with our old Cub Cadet.

The next day I pulled the gas tank off and drained it (there were a couple small chunks of trash/debris in the tank). I pulled out the gas filter and blew it out (there was a small chunk of trash in it). I checked the spark plugs and they were very black...I cleaned them up, checked the gap and put them back in. I checked the oil and it was perfect. I checked the air filter and it was clean and properly seated on the carb.

I took it out and ran it hard for 10 - 15 minutes. It ran great, and I put it back in the garage, thinking problem solved. I got it out this weekend and had the same issues. Sometimes I restart it and it runs fine for 15 minutes or so and the same things start happening. Other times, I have to let it cool for a few minutes or it will just die over and over.

Any ideas? Again, I appreciate any ideas anyone has.
Old 08-24-11, 07:20 PM
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Try loosening the gas cap when it starts surging and see if it gets better. It may be developing a vacuum in the tank because of a clogged gas cap vent. Otherwise I would say water and/or trash is in the carburetor.

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