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Thread: carb question

  1. #1

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    carb question

    i recently did a top end rebuild on my gp1200r and i also upgraded the carbs to a 1.5 n&s , 110 pilot jets , 120 main jets and 95 gram springs. i also have f/a installed with water socks. my low speed adjusters are 1 turn out on carb 1& 2 and i started out with one turn on carb 3 but when i did a test run i noticed that #3 carb was running alot leaner than the other two carbs. i did several test runs today turning out on the low speed adjuster 1/4 turn each test. i have the low speed adjuster 2 1/2 turns out now and there is still hardly any fouling on the spark plug electrode just alittle fouling on the bridge part of the spark plug. throttle response is crisp with no noticeable hesitation or signs of loading up. my high speed adjusters are all set at 1 1/2 turns out but i am afraid to put too much pressure on the engine until i figure out what is going on with this carb. cat converter is removed and d-plate is installed with sensor chip.i have pop-off set at 43 psi on all three carbs. any input would be appreciated.


  2. #2
    Moderator OsideBill's Avatar
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    Did you remove the accel pump? and if so, did you plug the nipple that feeds the accel pump on the bottom of carb #3?

    The screw should never ever need to be more than 1 turn out, especially when running water socks

  3. #3

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    i disabled the accel pump and i am using it for priming the carbs on start up. when i reasearch this set up i read that you can use the accel pump as a priming tool instead of installing a primer kit. will this set up harm the engine?

  4. #4
    Moderator OsideBill's Avatar
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    nope, but something else is wrong, if you can back that low speed screw out that far, and not change how the ski takes off. your sure it is the low speed you are adjusting? the one on the bottom side of the carb correct?

  5. #5

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    yes i am sure it is the low speed adjuster because when i installed the t-handles the accel pump was in the way for carb #3 and i had to put the old high speed adjuster screw back in.
    do think it could be something in the regulator or a bad gasket?

  6. #6
    Moderator OsideBill's Avatar
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    there is no regulator, I would be looking at the arm height for the Needle and Seat or the diaphragm. if it is not opening the needle you will not get enough fuel in there. also if there is an issue on the fuel pump side pulse line maybe diaphragm on that side etc. I do the drilled return mod so I know that if I have an issue in the fuel pump the other pums will make up for it.

  7. #7

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    when i was testing yesterday i ran the ski to about 3/4 throttle a few times and stopped the engine and checked #3 spark plug again and on the high side i did notice fouling on the spark plug. could a bad diaphram or a weak one cause the problem at low speed but work ok on the high side.

  8. #8
    Moderator OsideBill's Avatar
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    nope they work together so if you have the low wide open it adds more fuel to the entire circuit. set the low at 1 turn again and see how it pulls out of the hole. run the motor so it is good and warmed up then do a 1/4 throttle run and do a plug chop see what the plugs look like.

  9. #9

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    i set the screw back to one turn out but don't have enough time to take her down to the river today,gotta go to work in an hour. i'll let you know what happens maybe tommorrow afternoon. thanks Bill

  10. #10

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    went back to the river today ski seemed to run pretty good . ran the engine until warmed up, tried a hole shot right off the bat and ski accelerated good. i still haven't run it wide open but i have taken up to about 3/4 throttle for about 5 to 10 sec. i slowed down and ran at 1/4 throttle for about a minute and shut down the engine and checked the plugs. #1 was black, #2 was black and #3 was kind of a brown tint. i have read that the brownish color is what i should be looking for. i'm thinking now that the first two carbs are running rich and #3 may be ok.last year when i was running the stock intake duct i had a similar situation with the carbs but could not make any adjustments . thats when i decided to do the rejetting and install the f/a's and the rest of it. one more thing to mention i did notice that when i run on the high end of the rpms the engine will come up to speed but then the rpm's will start to drop off alittle. i still need to do a high end check with a fresh set of plugs. may get to that later this week. bill please let me know what you think.

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