Moded out js 440 problems.
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  1. #1
    PWCToday Newbie
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    May 2017
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    Illinois
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    Moded out js 440 problems.

    Let me start off with some background on the ski.
    1980 js 440. Got the ski about 2 weeks ago.
    Story was he bought it not running put some parts on it (new fuel lines,bars,finger throttle,starter)and didnt want to mess with it after starter gave him issues.

    So i got it and got the starter working,went through the carb,fixed the fuel lines that were *** backwards and after a little research i put a 0.030 welding tip in return line as a restrictor for the bn44 it has on it.
    Got it started and took it to the water and here are the problems i ran into.
    1.Its a ***** to start but idles and rides once it starts but dosent run good, idles fine though,and seems fine at 70 to wot.
    2.about 25 to 65 percent throttle it wants to just fall on its face, till i smack the throttle wide open. Started out with (HIGH 1.5 OUT) (LOW 1.0 OUT) (PILOT 1.0 OUT) and seemed like when i leand out the pilot and low it didnt even want to start, so i went out a quarter turn richer on the pilot and low and it fired back up and rode but still fell on it face inless you were at 75% throttle to wide open then it seemed fine. Battery died from turning damn thing over so much to get it restarted after making carb ajustments so didnt get to mess with ajustments that much.
    3. Didnt seem like much water was coming out of the exhaust, i took it out about 5 times for about 5 minutes at a tine and engine and exhaust felt hot but not hot enough to sizzle when i put water on it and you could touch the cylinder for a few seconds and it wont burn you, just seemed odd with how little water was coming out.

    Ski has.
    Ocean pro intake mani
    Bn44,ocean pro air filter
    L S exhaust mani
    West cost pipe,cone,and exit pipe
    Primer
    Pretty sure head work (175 psi each hole)

    Ocean pro kwik steer
    Ocean pro gas cap block off
    Ocean pro orginal exhaust block off
    Skat 16*

    So from some research ive done my questions are.
    Is the bn44 just to much for this ski even with its mods?
    And is it realy just in general just kind of a pain in the *** carb?
    How much water should i be seeing coming out of the exhaust exit wile riding?
    What temp should engine be operating at ?

    Im gonna take it to the water and tie it to the dock and stand next to it and realy take my time trying to tune it but figured id throw these qustions out there just because im eager to learn and cant get out there till this weekend.

    Thank you guys for any info and help.

  2. #2
    PWCToday Newbie
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    Re: Moded out js 440 problems.


  3. #3
    PWCToday Newbie
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    Re: Moded out js 440 problems.


  4. #4
    PWCToday Newbie
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    WA
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    Re: Moded out js 440 problems.

    44BN is excellent for stock-ish 550s with milled head & steel impeller.
    Seeing as your 440 is piped & the return is restricted, it should be a matter of opening up the low speed screw to get it to take off.
    Also the 44BN had some early issues with the carb circuits draining during shut down, the ski would fire up & run rich, people
    would start turning mixture screws looking to reset the carb when the problem was fuel draining internally into the engine.
    1 turn out on ANY 44BN mixture screw is too lean with alcohol-laced modern fuels.
    It's the black sheep of the Mikuni family, but my 1990 550 has a stock 44BN & runs fine with a OP vortex on it & restrictor in the return.
    EDIT: I'm curious which OceanPro filter you have on it, my vortex would never fit on a canted OP intake like you've got in your image.
    Good luck with it, hopefully it's just your low & pilot screws that need tweaking.
    Last edited by pepper22; 09-12-2018 at 02:13 AM. Reason: more info

  5. #5
    PWCToday Newbie
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    Re: Moded out js 440 problems.

    Yea i plan on geting some more tuning in this weekend, and i defiantly feel like it drai ing fuel into engine like you say because once i get it started if i turn it off but crank it back over right away it fires right up but if i let it sit for a few mins i have to crack the **** out of it and hold it wode open to start amd runs rich for a few seconds. I hear that using a pump diaphram from a yamaha carb will fix this. Have you heard of this ? I have the part nimber written down, might give that a try. Whats a canted intake ? And ill try and get a pic up of the air filter it has on it.

  6. #6
    PWCToday Newbie
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    Re: Moded out js 440 problems.


  7. #7
    PWCToday Newbie
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    WA
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    Re: Moded out js 440 problems.

    Thanks for the image!
    Looked like it was impossible to screw a Vortex on from the other angle from other image.
    I don't have knowledge about a Yamaha diaphragm helping with the draining/rich issue, i hope
    you're right about it, the '90 came with a revised fuel circuit that fixed it but the '86s where
    they first showed up had that unintended feature. Still a great carb to go plenty fast, just finicky. : (
    Seeing as everyone but me hates them, the 44BN bodies should be dirt cheap on Ebay, just not
    sure which late '80s 550 year they fixed that drain issue. I want to say '88? There has to be a 550
    freak somewhere around here who knows for sure. lol.

  8. #8
    PWCToday Newbie
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    Re: Moded out js 440 problems.

    No problem!! And yea i heard it from a older guy on a facebook page, i guess he use to race alot back in the day and said the yamaha diaphram solved that problem, everyone ealse just tells me to buy a bn38 or sbn38 lol.

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