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  1. #1
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    GPR\XLT Carb Upgrade\ Accelerator pump removal

    The Carburetors that came on the USA model 66V motors are originally set to meet EPA emissions guidelines. Yamaha achieved these goals by using the catalytic converter and leaning out the jetting on the carbs. The problem was they had no low end punch, to make up for this they added the accelerator pump. This gives a squirt of gas to the #1 & #3 carbs just off idle, and helped solve the lean low end issue.

    When tuners started upgrading these motors they removed the problem laden catalytic converter, and replaced them with a d-plate, They then opened up the air flow to the carburetors to allow the motor to breathe better, as a result rejetting became necessary.

    It was quickly discovered that the OEM jetting was extremely lean in the midrange, it was so lean that cruising at 4k-5k rpms for an extended period would cause an engine seizure. (infamous midrange seizure)

    As the jetting size was increased to remove the midrange lean condition and improve the top end performance another issue appeared "low end bog" this was now a rich condition from too much fuel. This condition was solved by removing the accelerator pump.

    The carb settings for the 66V motors that we see repeated over and over again, were developed quite some time ago. They have withstood the test of time and man.

    Carb settings with accelerator pump removed or disabled and after market F/A's (Flame Arrestors): These settings will work on both US and non US models.

    1200R Aftermarket F/A's (Flame Arrestors) chokes intact

      • 110 Pilot jets, 1 turn out on low speed adjusters
      • 120 main jets, 1-1/2 turn out on high speed adjusters
      • 1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure.
    1200R After Market F/A's chokes removed.

      • 110 Pilot jets, 1 turn out on low speed adjusters.
      • 125 Main jets 1-1/4 turn out on high speed adjusters
      • 1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure.


    Edit: 04/06/11
    Currently to my knowledge, there is no known jetting solution that will work for removing the accelerator pump and keeping the stock air box.

    Many members have tried this, and there has been no reliable jetting set-up that has been reported to have worked.

    If you have tried this and have been successful, please post your results for others to use. We welcome any proven solution.

    I have not and will not try this. I have never owned a stock air box, and I enjoy the benefits of the 10%+ performance increase provided by the after market FA's.

    If your hull is wet, fix the problem, add an aftermarket bilge and run water socks if necessary. Riva also made a nice splash gaurd for the carbs with after market F/A's.

    If your on a budget, remove the inlet piping and drill holes in your stock air box to let it breath.

    Please do not PM me asking for a solution for this. After explaining it countless times over the years, I have decided to post here in the hopes of never having to repeat myself again.
    Last edited by OsideBill; 01-31-2012 at 09:27 AM.


  2. #2
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    Accel removal

    There are a couple methods to remove or disable the accel pump. This is my preffered method.
    1. Remove Accel pump and all tubing.
    2. Install Mikuni cover plate (BN44/147 Cover, Stainless)
    3. Cap all accelerator hose nipples
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    Last edited by OsideBill; 08-17-2008 at 09:02 AM.

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  4. #3
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    The other popular method is to disable the accelerator pump. This is easy and you can use the pump manually as a primer. Simply remove the cam and replace the nut and washers. Just push on the accel pump arm and it gives a squirt of gas to prime the motor. (Only #1 & #3 get fuel)
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    Last edited by OsideBill; 08-31-2008 at 11:20 PM.

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  6. #4

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    I might have to do this!

    What other mods can i run with the:

    1200R After Market F/A's chokes removed.
      • 110 Pilot jets, 1 turn out on low speed adjusters.
      • 125 Main jets 1-1/2 turn out on high speed adjusters
      • 1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure.

  7. #5
    There is no winter in Hawaii!
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    I did the second method, removed the cam. I have yet to reach in there to give a squirt. I tried after I put it together and the stinger is in the way and I can't reach it on the XLT. I saw a post somewhere that someone put a nylon tie on the end of the lever to grab and pull. I haven't needed it, good thing!

  8. #6
    If your not doing something, its hard to screw up.
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    Bump

  9. #7

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    I'm intrigued! I'm just getting into a few "clean-ups" for my 2000, WaveRunner 1200 XL LTD. Replaced a failed (catastrophically!) CatConv with a D-plate and Chip; am removing the oil injector pump and going the premix route; am installing a primer kit; and am re-building the carbs.

    From what I read of your fascinating and easy-to-follow recommendation, I'm not sure what the jetting would be if I have the D-plate, but retain the stock F/A and intake plennum. What is your experience with this combo?

    Also, I'm in Florida. Have any of these mods been done successfully in our "high density-altitude" conditions?

    Tnx!

  10. #8
    May the 2 Stroke Live On
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    When tuners started upgrading these motors they removed the problem laden catalytic converter, and replaced them with a d-plate, They then opened up the air flow to the carburetors to allow the motor to breathe better, as a result rejetting became necessary.

    It was quickly discovered that the OEM jetting was extremely lean in the midrange, it was so lean that cruising at 4k-5k rpms for an extended period would cause an engine seizure. (infamous midrange seizure)



    The carb settings for the 66V motors that we see repeated over and over again, were developed quite some time ago. They have withstood the test of time and man.


    I'm a new member so i haven't quite figured out how to quote properly and all that..however, i've got a 99 66v motor in my 1200 xl..Cat was falling apart, so i ordered the D-plate from Riva Yamaha and the dummy sensor...

    Now, will i have to worry about a lean condition at various RPMs with the reduced backpressure of the d-plate? i'm using the stock intake plenum and don't really plan any other mods for this ski. I also still have the stock accelerator pump in place and i haven't touched anything on the carb yet.. Will i have to richen it up the low speed jet and high speed jet with just the d-plate? Still have stock oil injection in place as well and it all works wonderfully. Cat's out of the bag though thank God!

  11. #9
    May the 2 Stroke Live On
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    Pics from Above Post..
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  12. #10
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    You will be fine if you are just running the d-plate

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