Carb tuning. JS440.
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  1. #1
    Resident Guru skuzzlebutt's Avatar
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    Carb tuning. JS440.

    Can someone help me tune my carb. I have no problem doing it in the water like your suppose to. Heres a picture of the carb I have. Can someone tell me what kind it is as well?

    Basically the ski will run fine for a while then it will become hard to start and once it finally does start it deosnt get past half throttle and then dies. So basically i'll be trying to kneel on it then i'll bite the dust.

    I had a post on here a few days ago and was told it looks like my engine is running lean.

    I was told to check the check-valve and im going to buy a new one for the heck of it but im not 100% convinced thats the problem.

    One last thing is it doent want to stay running when i fall off of it. It's basically doenst idle in the water. I have yet to see it circle when i fall off of it.
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  2. #2
    Resident Guru skuzzlebutt's Avatar
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    Re: Carb tuning. JS440.

    I forgot to mention that the first tank of gas was running a premix of 32:1 could that be the problem? What should I run it at 50:1? Could too much oil becausign power issues? But then again my plugs are light tan and dry so im lost....

  3. #3
    PWCToday.com Is My Home Away From Home tjmonsen5's Avatar
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    Re: Carb tuning. JS440.

    32:1 is way too much oil. 50:1 to 40:1 is what you want. But that shouldnt really affect performance too much. It looks like the "safety" caps are still on the adjustment screws so your settings "should" be stock. If you are running lean, pull the caps off of the adjustment screws and turn them out a little bit.

    Mikuni BN 38
    If You're Not Running PJS Parts, You're Chasing Someone Who Is.

  4. #4
    Resident Guru Big Dad's Avatar
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    Re: Carb tuning. JS440.

    The stock settings for that carb,a 44bn(round body) mikuni,are low speed(lower right)-1&1/16,pilot(lower left)-1&5/16 and high speed(upper left)-15/16.These are the turns out from being lightly seated.Are you still running the rev limiter?If not,you'll need a restrictor "pill" in the return line.The rev limiter solenoid has a small restriction built in so the carb doesn't run lean on the high end.If you need one,you can make it out of 1/4 in. brass round stock.Cut it 1/2 in. long and drill a .050 hole lengthwise in it.Put it in the return line up by the nipple on the carb where the return line goes to the tank.The round stock and the drill bit can be bought at a hardware store. Jim

  5. #5
    Frequent Poster Skeach's Avatar
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    Re: Carb tuning. JS440.

    Quote Originally Posted by skuzzlebutt
    I forgot to mention that the first tank of gas was running a premix of 32:1 could that be the problem? What should I run it at 50:1? Could too much oil becausign power issues? But then again my plugs are light tan and dry so im lost....
    I'm no expert, but I read that for the first 2 tanks of a ski's life, it should have a mix of 25:1, and then 50:1 after that. So while it is too much oil, it probably shouldn't affect it like that.

  6. #6
    Top Dog hilljt's Avatar
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    Re: Carb tuning. JS440.

    Its a BN44 like Big Dad said, not a 38. The 44 had 4 four bolts on top, 38 had 3.......yours has 4.

    Follow Big Dad's advice to a T!
    Last edited by hilljt; 06-14-2008 at 12:10 PM.

  7. #7
    Resident Guru skuzzlebutt's Avatar
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    Re: Carb tuning. JS440.

    big dad.... there is no rev limiter in the elec. box. i didnt know that the 81 440s had it... Should i still make a restrictor. does any one have a picture. could this restrictor be causing some of my problems? its running too lean at high rpms?

  8. #8
    Resident Guru skuzzlebutt's Avatar
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    Re: Carb tuning. JS440.

    And a .050 hole is a 1/20" dril bit correct?

  9. #9
    Resident Guru skuzzlebutt's Avatar
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    Re: Carb tuning. JS440.

    This isnt the stock carb on this js440 is it?

  10. #10
    Top Dog hilljt's Avatar
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    Re: Carb tuning. JS440.

    Quote Originally Posted by skuzzlebutt
    big dad.... there is no rev limiter in the elec. box. i didnt know that the 81 440s had it... Should i still make a restrictor. does any one have a picture. could this restrictor be causing some of my problems? its running too lean at high rpms?
    Only the electric part would be in the ebox, the valve would be behind the sediment bowl. Stock, no the 81 440 did not have a rev limiter.

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