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Thread: gpr missing

  1. #1

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    gpr missing

    i have a yamaha gp 1200 waverunner that i recently rebuilt the carbs with stock rebuild kits. put the boat in the water last week and the boat ran great for about an hour then seemed to have a slight miss in between 3k and 5k rpms, the boat will run wide open flawless but when i back off alittle sometimes it seems to run fine at those rpms and then sometimes it will start to miss at those rpms but if i go ahead and give it the throttle to wide open it runs fine. this boat is an older model and the motor has never been rebuilt as far as i know. i did remove the cat and installed the d-plate and sensor chip. the boat is a 2000 yr model. i also did a comp check on the motor and got readings of 95,100,100 on a cold engine and with the engine warm i got readings of 100,110,105. i also converted the motor to premix and removed the oil pump. can anyone help me with this problem ?


  2. #2
    Prism's Avatar
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    Sounds like a sparkplug, or sparkplug wire issue. Try changing the plugs. If that dosent help, ride it with the seat off just before dark and check for arcing. You could run your hands around the plug wires on the trailer with it running. Just remember there is a high probability of getting zapped by grabbing wires that possibly are bad.

  3. #3

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    thanks for the info, does the engine need to have a load on it to uncover a bad spark plug wire? i was thinking about hooking a hose to it and run it in the driveway after dark. i put a new set of plugs in it the other day, i will put the boat in the water this afternoon to check it out.

  4. #4

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    Have you ever done carbs on one of these before ?, did you set the pop off psi?, they can be tricky if you have never done them, did it run this way before you did them?

  5. #5

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    no, i installed stock rebuild kits into the carbs and i used a popoff gauge in the 0-60 psi range and could not get the needle valve to popoff, i read in some other threads that the stock popoff on the 1.2 needle could be in the 80-85psi range and i did'nt want to spend the money on a new gauge or any carb parts.before i did the carbs i could hardy keep the boat running, i didn't change ay of the high and low speed adjusters from the original factory settings. the carbs still have the tamper evident caps on them.

  6. #6
    I have the same year model...should have left oil pump on and premix and run pump...I put oil pump block on mine and ran premix only and shattered #3 piston from lack of oil/gas from carb..so rebuilt it and put pump back on which sucked because had to move motor back to reinstall but i always run 50.1 and pump i know its alot of oil mixture but runs great with no spark plug fouls..because #3 wants that oil..better safe then sorry..I run my raider 1100 same way premix and pump...had no probs for years still runs tip top..I had a spark plug wire grounding on block that caused that on mine..

  7. #7
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