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  1. #1

    Question new 2000 gp1200 running rough under 5000 rpm

    Hello,

    I replaced my old kaw 650 stand up with a gp1200 this summer and I need a little help getting it running right. I have read the forums untill my brain is mush and I hav a couple questions now.

    First the ski was just repaired by the PO for a burnt #3 cyl. new piston and rings and converted to premix. it has a D plate and no mods were made to the carb. that is as much as I know about the engine.

    The problem is when cold it bogs terribly until it warms up then it holeshots just fine. the entier time its running it runs rough until it hits right about 5k rpm then runs great. Makes me believe from what i have read that the lower stage mixture is a bit to lean. I believe the servo for the power valves is working correctly but that is only from watching it move around and the fact that the holeshot is better after it warms up.

    My current thought is I probably need to drill out the stock mixture blockages and open up the jets a little more as is suggested in many of the posts I read. My questions are as follows.

    1 does the diagnosis sound correct for the symptoms?

    2 does the cure sound like the right one? do the jets need to be upsized in that powe range as well or just the screws opened up a bit?

    3 I also read that when running the premix you should disconnect the accelerator pumps. I dont understand why going from injection to premix would require less fuel on the holeshot unless you were really upsizing the jets. maybe i missed something in reading that one but its been bothering me.

    anyway, thanks for all the great posts and if you could help me with my diagnosis and cure I would be thankful. I am headed out now to get a better look at the mixture screws and see if i can do it in the hull or if i need to pull the carbs out and take them in the garage. I think i can get jets from the local yamaha guys here if i need to upsize them but i am hopeful the adjustment will take care of it. Not looking to really gain a lot of power this round just make it a very solid enjoyable ride for the wife and kids. power mods will probably start over the winter...

    Thanks


  2. #2

    Join Date
    Feb 2012
    Location
    Wake Forest, NC
    Posts
    91
    So your profile says its a gp1200 xlt.... In 2000 they switched to the gp1200r.

    Anyway, could be low compression, carb issues, power valve issues. Need to start by checking those things out and eliminating one by one

  3. #3
    I did download the manual as suggested many places, thanks for that!

  4. #4
    #3 just got a new piston and rings before I purchased it, all 3 good compression now and on 2nd tank of fuel.

  5. #5

    Join Date
    Feb 2012
    Location
    Wake Forest, NC
    Posts
    91
    When you say compression is good, what are they reading? How are you doing the check? Cold motor, only 1 plug out with WOT?

  6. #6
    122# 122# and 119# on the rebuilt cyl. no run time on it when it was checked by the shop that did the repair. I have not put my own gauge on it yet. Repair shop gave me the compression #s. power valve servo is operating as the manual explains it should, it cycles after shutoff and changes position when the revs hit a certain rpm. runs like a top over half throttle so I would not suspect compression to be an issue or the issue should be the same througout the rpm range. happy to runa compression test next week when i am home with my good tools but this week I dont have one me.

    I should take a ride with the seat off and watch the power valve cycle to see if it does change position at the same rpm as the engine starts to run better but it just sounds like a carb issue from what i have read. could be wrong...

  7. #7

    Join Date
    Jun 2011
    Location
    hopewell,Va.
    Posts
    139
    if not already done,you should pull the carbs and inspect clean and put rebuild kits in. if you run f/a's you will need to rejet the carbs, and put in new needle and seat with new springs. if running stock breather you should not have to upgrade but do buy new stock jets and needle seat combo. you should also check pop-off and reset to factory specs. on this forum there is a pop-off chart in the how to section. correct carbureation is essential on these gprs. good luck.

  8. #8

    Join Date
    Jun 2011
    Location
    hopewell,Va.
    Posts
    139
    don't mean to hack your thread seanrupp but hows the ski running e46.

  9. #9

    Join Date
    Feb 2012
    Location
    Wake Forest, NC
    Posts
    91
    Quote Originally Posted by rich.allen View Post
    don't mean to hack your thread seanrupp but hows the ski running e46.
    Runs awesome! Tweaked with carbs a bit and got it running awesome. Unfortunately may have to sell to free up some cash and its the most logical. We'll see what happens.

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