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  1. #1

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    Sudden RPM drop off around 3900

    My 2000 xl1200 ltd is running perfect except for an occasional 400 or so rpm drop when running about 3900/4000 rpm. It's a quick drop and returns to higher rpm immediately with throttle. It started several hours ago with a carb rejet after a d-plate install. A mechanic did the work so I don't know what size jets he installed. The engine will also occasionally bog a little or suddenly rev up to 6000 at around 4500 rpm.
    Am I harming the engine if I continue to run it and monitor it? I'm planning on a carb rebuild with a primer kit install this winter.(maybe 6 or 7 more running hours from now) The ski has 41 hours total time.


  2. #2
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by LakeDog View Post
    My 2000 xl1200 ltd is running perfect except for an occasional 400 or so rpm drop when running about 3900/4000 rpm. It's a quick drop and returns to higher rpm immediately with throttle. It started several hours ago with a carb rejet after a d-plate install. A mechanic did the work so I don't know what size jets he installed. The engine will also occasionally bog a little or suddenly rev up to 6000 at around 4500 rpm.
    Am I harming the engine if I continue to run it and monitor it? I'm planning on a carb rebuild with a primer kit install this winter.(maybe 6 or 7 more running hours from now) The ski has 41 hours total time.
    Get it checked you should be about 7000 plus rpm's running that low is no good for the engine.

  3. #3

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    Jim or Mike: It does run to 7000 rpm no problem and stay there. It just has this occasional stall at around 3900 like when I want to go slow around the dock area. The plugs are new and clean...

  4. #4
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by LakeDog View Post
    Jim or Mike: It does run to 7000 rpm no problem and stay there. It just has this occasional stall at around 3900 like when I want to go slow around the dock area. The plugs are new and clean...
    Sorry my mistake, Sounds like the carbs. are going to have to be taken apart and gone over. Also make sure your power valves are working correct, If you are getting over 7000 rpm's you could ride it till you are ready to build them.

  5. #5

    Smile

    Your jetting and or power valves are off or not working properly, they are electrically opened and when they open its like having a ported cylinder which gives you much better top end.Normally with yamaha they open smoothly and you dont notice them,However since your problem started after dring and jetting change I would suspect that area first.did you modify your intake air box after jetting change??>Marvin

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