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JD 425 running rough

Discussion in 'Mechanic and Repair' started by Hitman-98, Jul 24, 2008.

  1. Hitman-98

    Hitman-98 LawnSite Member
    Posts: 5

    I have a '99 John Deere 425 AWS with a Kaw 20hp engine. Last year the thing started going through stints of runing rough. It only happened a couple of times at the end of last year. Starting this year the dang thing ran great, no problems at all until last week. It started it again and now seems to be doing it all the time. If I have the mower ingaged it loses power and shakes until it stalls. I can here the difference in the motor, it seems like it is missing.

    I have changed fuel filters and plugs, but it did not help. The plugs I took out looked fine and did not look like either of them were not firing.

    I was told to change out the selinoid that is on the back of the left side of the engine. It has wires going to both coils and the starter. I was told this was a cheap thing to try.

    Anyone have any other suggestions?
  2. Phil G

    Phil G LawnSite Senior Member
    Posts: 843

    Initially, if the engine is running fine when it's in neutral then I would suspect overloading on the deck belts or blades. With the engine turned off, reach under the deck and see if you can turn the blades by hand. They should have resistance but turn smoothly with no tight spots.
    Let us know.
    Good luck Phil :)
  3. Hitman-98

    Hitman-98 LawnSite Member
    Posts: 5

    It does it at start up, when it is doing it.

    I replaced the part I was talking about...on the receipt it is called a "module". After installing this part, it started and ran great. I ran it around the driveway a few times and then parked it because it was dark. I got up today and syphoned all the gas out and put high grade in just incase it might have also been bad gas. It started and ran good and after one trip around the yard it started acting up again. This has to be electrical somewhere, since it comes and goes. It always seems to go away for a brief time and then when it comes back it stays. I try something...like change the plugs, it may run okay and then bad again.

    I think I am going to have to take it in.
  4. AmsoilPower

    AmsoilPower LawnSite Senior Member
    Posts: 938

    The 425 is known to have camshaft issues. The stock cam is a nylon/plastic material and develops alot of play in the rivots that hold it toghether. I have seen 6 or so with this issue. The replacement cam is all steel now. Your symptoms sound like this is the issue. Hopefully you can do it yourself, or else it will be a costly repair. Cam is about $80 itself.
  5. Hitman-98

    Hitman-98 LawnSite Member
    Posts: 5

    Well, I was messing with it again last night and I didn't have spark on the left side. So today I went and got a new coil and installed it. Good spark on both sides, so I button it up and take it for a test run. Same thing, slows to a crawl and studders under load. It is not just the mower being engaged. If I just step all the way down on the hydrostat, it bogs down. Could it be a hydro pump going bad?
  6. Hitman-98

    Hitman-98 LawnSite Member
    Posts: 5

    Before I gave up and took it to the shop, I pulled both plugs and turned it over to check for spark. Right side had spark the left side didn't. So I went and got a new coil, installed it and had good spark on both sides. Put the plugs in and fire it up and still running bad. I then pulled the plugs and checked for spark again and I was back to no spark on the left side. Could that new coil go bad on the first try?
  7. jeepermat

    jeepermat LawnSite Member
    Posts: 4

    Did you ever figure this out?
    I am having the exact same problems with my 425, it started running rough, and was hard to start, now it wont start at all. As far as I can tell there is no spark at either plug. I do have power at both coils though.
  8. Albery's Lawn & Tractor

    Albery's Lawn & Tractor LawnSite Bronze Member
    Posts: 1,675

    Sounds somewhat similar problems as we use to have on our 425 as well. Ours ended being the carb was sending to much fuel causing the plugs to foul out. Dad pulled it off, rebuilt the carb and 2 new plugs and its been running great for the past 50 hours or so.
  9. jeepermat

    jeepermat LawnSite Member
    Posts: 4

    The plugs in mine are brand new, after trying to start for a while they are not fouled. However there is no spark coming to them.
  10. Albery's Lawn & Tractor

    Albery's Lawn & Tractor LawnSite Bronze Member
    Posts: 1,675

    When you pull them out is there gas on the plugs? If you've been constantly trying to start it, it seems it would have quickly gas fouled the plugs.

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