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  1. #1
    PWCToday Regular Firebird!'s Avatar
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    Apr 2006
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    Lakeland, FL
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    42
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    139

    Carburator tuning.

    Here is me again with carb tuning.
    Got a fresh rebuilt engine and rebuild carbs.
    Got engine broken in and adjusting carbs now.
    In general I am satisfied how engine works. I think I had some hesitation at the beginning of the throttle - rpms were rising slowly and then jumped from about 4500 to 5000. Changing pop-off from 50psi to 30psi seemed to fixed it.

    Ok, back to the topic. Trying to do it by the book, starting with idle. I was able to find that sweet spot adjusting Low Speed adjusters, watching my digital tachometer, to the point where little more or little less would screw up the rpms. That worked for the 1st(mag) and 2nd(center) carbs. For the 3rd(PTO) I couldn't get it. I did see some changes in rpms when I went to almost closed or way open. Also 1st and 2nd cyclinders felt quite warm during idle when the 3rd was pretty much cold. Also when inspecting the plugs - the 1st and 2nd were dry, the 3rd is wet. The pics were taken after about 5 min of idling.

    What am I missing here?

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    '99 Yamaha SUV1200
    '02 Kawasaki Ninja ZX6R
    '12 BMW 650i Convertible
    '12 Mercedes GL350 Diesel
    Sold '99 Pontiac Firebird, '02 Ford Explorer Eddie Bauer, '04 Mercedes SL500 '09 GMC Acadia, '14 Acura MDX

    $8 pop-off pressure gauge

  2. #2
    PWCToday Guru
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    Sep 2013
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    Bennettsville, SC
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    47
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    347

    Re: Carburator tuning.

    Unless you have a highly modified motor, and I do mean HIGHLY modded, it is best to stick to what the manufacturer set the carbs to at the factory. Exception being the GP1200R, there is a jetting solution that works great for them. What model ski do you have? Once we know the model, you can get much more help.
    Last edited by butterbean_29512; 05-27-2018 at 08:57 AM.

  3. #3
    PWCToday Regular Firebird!'s Avatar
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    139

    Re: Carburator tuning.

    It's Yamaha SUV. With 65U non-pv motor. Nothing highly modified, just K&N FA and oil pump removed. I'm leaning towards the ignition coil being bad for that cylinder, which I'm going to check next. Just wanna see what you guys are thinking.
    Quote Originally Posted by butterbean_29512 View Post
    Unless you have a highly modified motor, and I do mean HIGHLY modded, it is best to stick to what the manufacturer set the carbs to at the factory. Exception being the GP1200R, there is a jetting solution that works great for them. What model ski do you have? Once we know the model, you can get much more help.
    Sent from my SM-N950U using Tapatalk
    '99 Yamaha SUV1200
    '02 Kawasaki Ninja ZX6R
    '12 BMW 650i Convertible
    '12 Mercedes GL350 Diesel
    Sold '99 Pontiac Firebird, '02 Ford Explorer Eddie Bauer, '04 Mercedes SL500 '09 GMC Acadia, '14 Acura MDX

    $8 pop-off pressure gauge

  4. #4
    PWCToday.com Is My Home Away From Home
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    May 2007
    Location
    Arkansas
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    2,260

    Re: Carburator tuning.

    Check for play in your throttle shafts. 55psi is the best pop off if your run am flame aresters.
    Outside bill carb up date is a must imo. Always genuine Mikuni parts. Get T handle adjustment screws. Check the fuel pump check valves probably have a creased one or two. I've creased them first time out just like bill says. I'm very hard on the 65u I run and been trying to get cards tuned perfectly for the last 4 years.
    I put in new needle and seat a couple two three years ago and I'm installing new genuine mikunis again this week. I also have a new intake manifold that's going to allow me to turn the carburetors 45 so I can link shafts. It will help keep from wearing the shaft bushings out so quickly.

    I wouldn't have taken off the variable speed oil pump they save tremendous amounts of oil if you do much mid low range RPM time
    Last edited by driftmaster; 05-28-2018 at 12:50 AM.

  5. #5
    PWCToday Regular Firebird!'s Avatar
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    139

    Re: Carburator tuning.

    Ok, I got checked the spark with the spark gap tester. I observed the spark at all three cylinders but it seemed that specially at third (PTO) it was intermittent.

    So I built the peak voltage adapter and checked the output peak voltage of CDI unit. It was below the spec. around 70v.

    Then I checked the Charge coil peak voltage. Below the spec. - around the 70v again.

    While I was there checked the pulse coil voltages got 2v, 3v, 4v. (below, right on, above)

    But resistance of all coils is within the spec.

    Is it possible? Does it still mean that I have a problem there?

    Sent from my SM-N950U using Tapatalk
    '99 Yamaha SUV1200
    '02 Kawasaki Ninja ZX6R
    '12 BMW 650i Convertible
    '12 Mercedes GL350 Diesel
    Sold '99 Pontiac Firebird, '02 Ford Explorer Eddie Bauer, '04 Mercedes SL500 '09 GMC Acadia, '14 Acura MDX

    $8 pop-off pressure gauge

  6. #6
    PWCToday Regular Firebird!'s Avatar
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    Apr 2006
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    Lakeland, FL
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    42
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    139

    Re: Carburator tuning.

    Ok, replaced the charge coil and pulser coils from the used unit I got from eBay. Measured over 110v on a charge coil now (was about 70v). Checked the sparks with spark gap tester. The sparks now beautiful: brigher and consistent on all cyclinders. What a change!

    Still have 2, 3 and 4volts on pulser coils, don't know why that difference - but since I see sparks - it is probably still working.

    Sent from my SM-N950U using Tapatalk
    '99 Yamaha SUV1200
    '02 Kawasaki Ninja ZX6R
    '12 BMW 650i Convertible
    '12 Mercedes GL350 Diesel
    Sold '99 Pontiac Firebird, '02 Ford Explorer Eddie Bauer, '04 Mercedes SL500 '09 GMC Acadia, '14 Acura MDX

    $8 pop-off pressure gauge

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