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  1. #1
    PWCToday Newbie
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    Carb jets on dual keihin 40 mm with three jets

    I'm doing a rebuild on my x2 I got a nice 750 to put in it and I have an srx wet pipe also. The only other modifications is a drilled water box, prop, and aftermarket flame arrestors. Does anyone know what size jets I should use on this set up. The manual for the pipe says 152.5 main and 80 pilot. But says nothing about your carb if it has a third jet. Any suggestions would be appreciated

  2. #2
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: Carb jets on dual keihin 40 mm with three jets

    the stock jetting is 72 pilot 45 mid and 135 main. probably could leave the mid at 45 and be fine with the jetting you listed. im running 3 jet keihins on a 750 with a modded westcoast 650 pipe. im running 78 pilot, 50 mid and 140 mains. also depends on the popoff youre running. i have gutted stock flame arrestor with the rubber ends removed and 1 screen instead of 3. i had to use the shortest spring in the rebuild kit when i went through the carbs with the jetting i have. the settings you have might be for the sxr mikuni carbs. keihin didnt make jets with the .5 increments.
    91 440; PJS Viper 7000, jetsport exhaust mani, factory full pipe, coffman waterbox,solas 17*, jetco worked 440 pump, ocean pro nozzles. shredmaster ocean rideplate and grate combo, wide tray, footholds, deep strake mod, driveshaft fill,650sx quick turn

    build thread part 1: http://www.pwctoday.com/showthread.php?t=331343
    build thread part 2: http://www.pwctoday.com/showthread.php?t=364872
    build thread part 3: http://www.pwctoday.com/showthread.php?t=396154

  3. #3
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    Re: Carb jets on dual keihin 40 mm with three jets

    Thanks very helpful I have 150 and 155 mains that's the closest I could find. Don't know which would most likely be better to run, I'm also rebuilding them and from what I was reading what thinking about changing the mid to 50 also. And which of the two is the mid and low jet?

  4. #4
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: Carb jets on dual keihin 40 mm with three jets

    Those are either instructions for a 750 sx / sxi wet pipe with 2 jet Keihins, or sxi with dual Mikunis as fastgt said. Either way they are not for 3 jet Keihins. 150 or 155 mains would be extremely rich for the 3 jet carbs. What you actually need to be closer to is xir jetting. The xir had the 3 jet Keihins and I believe I posted up instructions in the xir bible I created in this Kawi section. I can't remember them off the top of my head.

    We have about half a dozen skis which have run these settings and they are all at 78, 50, 132. The mid jet is the one which is 45 stock. I can't remember the location of which is which, there's threads on here which have that info. I'd check the 3 jet Keihin carb thread.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
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    1987 WJ650:
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    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
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  5. #5
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    Re: Carb jets on dual keihin 40 mm with three jets

    What our your screw ajustments for this set up?

  6. #6
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    Re: Carb jets on dual keihin 40 mm with three jets

    Hey, im running a 750 sx with 3 jet keihins.
    I'm runnig 80 pilot, 50 mid and 145 mais. Popoff 20 psi with 2.0 needle and Factory Pipe Mod Chamber.
    My 750 is running 7150 rpm using 12/17 skat-track impeller.

  7. #7
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: Carb jets on dual keihin 40 mm with three jets

    both screws are at around 1.5 turns out. mine wont even start below 1 turn out.
    91 440; PJS Viper 7000, jetsport exhaust mani, factory full pipe, coffman waterbox,solas 17*, jetco worked 440 pump, ocean pro nozzles. shredmaster ocean rideplate and grate combo, wide tray, footholds, deep strake mod, driveshaft fill,650sx quick turn

    build thread part 1: http://www.pwctoday.com/showthread.php?t=331343
    build thread part 2: http://www.pwctoday.com/showthread.php?t=364872
    build thread part 3: http://www.pwctoday.com/showthread.php?t=396154

  8. #8
    PWCToday Guru scottw090's Avatar
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    Re: Carb jets on dual keihin 40 mm with three jets

    there is a lot of information here, although it may take a few read-throughs to grasp it all. I think wmazz on here has some blog articles that take carb tuning from the bottom up. worth a read too.

    http://www.pwctoday.com/showthread.php?t=400156

    I'd see if you can get it running on the stock jets and if you run out of screw adjustment (more than 2 1/2 turns), change jets. remember, you are tuning for target RPM against your prop.

    FWIW, I have upped all three jets on my set, with a factory limited pipe and prok filters. 80/50/147 i think. I'll be bumping the lows up another jet next time i have the carbs out. The ski runs good as is, but low screws are very open. I am turning a stock sxr prop 13/18.

    its pretty dang fast. I was in a grudge match against my brother's buckshots on his 750 this summer. He had me out of the hole, but i would catch him on straights.

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