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  1. #1

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    2000 Yamaha GP1200R won't run higher than 5000rpm

    I have a Riva modified 2000 Yamaha GP1200R. It has had an issue I can't seem to figure out over the past 2 years. It won't go faster than 5000rpm sustained. When I first start out it will peak up to 6000rpm then back off and not get above 5k. It feels like it's bogging out and it will attempt to go faster but ultimately will not run faster than 5k for more than a second or two. It will run all day at 4500-5000 perfectly and once it stumbles above 5k it re-catches at 4500 and runs fine again. It starts easily and idles great. It has the d-plate modification and the oil pump removed and has a primer installed.

    It has about 210 hours on it, has compression between 115-125 in all 3 cylinders. I had the carbs rebuilt at the beginning of the year in 2020. I checked the fuel pick up in the tank and it was fine looking. I also replaced the in-line fuel filter and checked the water separator.

    I've tried to pump the primer when at 5000rpm and this doesn't help it. All 3 plugs are properly gap-ed and look good.

    I really don't want to pull the carbs as they were rebuilt less than 4 hours of run time ago.

    What should I try next? Remember, this starts perfectly and runs perfectly up to 5000rpm where it starts to stumble.

    I'm really not sure where to look next.
    Last edited by top-pop; 08-25-2021 at 12:42 PM. Reason: Fuel filter added


  2. #2
    Myself's Avatar
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    My first guess would be the PV servo motor has quit.

  3. +1 by:

    WFO

  4. #3

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    You know I was thinking of that! I don't hear the sound anymore as that would normally move. What would be my next step to check that?

  5. #4
    Myself's Avatar
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    I always just fire the engine up, give it 10 seconds warm up, blip 1/2 throttle a time or 2, then shut it of..........watch for cable movement. If there is none...it's dead.

  6. #5
    Quote Originally Posted by Myself View Post
    My first guess would be the PV servo motor has quit.
    Yes sounds related to the power valves, also check the cables adjustment and linkage between cylinders

  7. #6

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    Ok, fired it up and the servo was working fine. I guess I couldn't hear it. The pulley moves as the cables push and pull. I watched between the cylinders and all both of the connectors moved in and out too.
    Any other ideas?
    Should I assume that since I tried to dump more fuel into it with the primer and it still couldn't stay above 5000rpm that it isn't fuel related, but air or spark related?

  8. #7
    Happily Self-Employed WFO's Avatar
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    Quote Originally Posted by top-pop View Post
    I have a Riva modified 2000 Yamaha GP1200R. It has had an issue I can't seem to figure out over the past 2 years. It won't go faster than 5000rpm sustained. When I first start out it will peak up to 6000rpm then back off and not get above 5k. It feels like it's bogging out and it will attempt to go faster but ultimately will not run faster than 5k for more than a second or two. It will run all day at 4500-5000 perfectly and once it stumbles above 5k it re-catches at 4500 and runs fine again. It starts easily and idles great. It has the d-plate modification and the oil pump removed and has a primer installed.

    It has about 210 hours on it, has compression between 115-125 in all 3 cylinders. I had the carbs rebuilt at the beginning of the year in 2020. I checked the fuel pick up in the tank and it was fine looking. I also replaced the in-line fuel filter and checked the water separator.

    I've tried to pump the primer when at 5000rpm and this doesn't help it. All 3 plugs are properly gap-ed and look good.

    I really don't want to pull the carbs as they were rebuilt less than 4 hours of run time ago.

    What should I try next? Remember, this starts perfectly and runs perfectly up to 5000rpm where it starts to stumble.

    I'm really not sure where to look next.
    "Riva Modified" may have an aftermarket ecu in there, and they are known to fail. The Advent had little dip switches to change features

  9. #8

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    Quote Originally Posted by WFO View Post
    "Riva Modified" may have an aftermarket ecu in there, and they are known to fail. The Advent had little dip switches to change features
    How would I check the ECU? I'm the second owner. The modifications i see are the cylinder-kegs, d-plate, ride plate and carb intakes.
    Would an ECU issue not be prevalent throughout the whole power-band?
    I'm just not sure what my next diagnostic test should be.

    Is it possible to be a coil issue that only happens at higher rpm? When i pump the primer at 5000rpm it just seems like it's getting flooded but it won't sustain RPM over that level.

  10. #9

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    The ecu performs many tasks, one is to open the PV’s at or above a certain RPM. Ride with the seat off and see if they’re actually opening. Check the returns to make sure you don’t have a blockage, just because the carbs were rebuilt a year ago doesn’t mean something didn’t get in there and cause havoc.

  11. #10

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    I'll do the ride with the seat removed. When I had the carbs rebuilt it was specifically to solve this issue back in 2020. I assumed they needed rebuilding due to this issue. Before and since it has not run properly so I don't think anything has changed with the carbs. I do need to check the return lines though. Just not sure how to do this easily or how to test for blockages.

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