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  1. #1

    GP1200 High, low, mains, for Arrestors & Oil Block off

    Hey guys. I am getting frustrated out here. Have GP1200 with flame arrestors and oil block off. Can some1 give me the corrects specs for high, low adjusters and main. I am running very lean on top. Came out a full 2 1/2 turns. No more to go. What size jets should i be running? Thanks.


  2. #2

    Join Date
    Jun 2010
    Location
    Boston MA
    Posts
    25
    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 1-1/2 turn out on high speed adjusters
    1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure

  3. #3
    CJ River Rider's Avatar
    Join Date
    Jul 2008
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    Quote Originally Posted by warvick View Post
    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 1-1/2 turn out on high speed adjusters
    1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure
    I'm no expert but isn't he talking about the 65U engine? He says 98 GP1200.

  4. #4

    Join Date
    Jun 2010
    Location
    Boston MA
    Posts
    25
    Uuupss my bad, this is settings for 66V

  5. #5

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