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  1. #1
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    Base settings on A dual 38 set up.

    I'm working on a westcoast themed build found Here:
    http://www.pwctoday.com/showthread.php?t=469713

    So here is what i do know, its a Westcoast RC520 Race Cylinder. It is ported, it has a nice taper/cutout at the top of intake. it used 750 reed valves. the cylinder is similar to a pjs reed cylinder.
    its got a 5 ring westcoaST EXHAUST w/ westcoast waterbox, and it'll be running rear ex. It'll probably be running a compression of 195-205.

    carb jetting right now are P 65 and H 85 ( i think ) So the question is what is the jetting i should be using? and what should my first screw ajustment be at?

    thanks
    90' 550SX "Shaved head, .5mm+ Wiseco pistons, SBN 44, Kerker exhaust, Mariner waterbox, WestCoast OS Gas Tank, extended ride plate,(440 pump) 16deg SS Skat imp."
    WIP - 83' JS550 " .5mm+ Wiseco pistons, WestCoast: Head, rc520 reed cyl, 7 Ring Exhaust, Ext Ride plate, Ex Manifold, 2x Velocity stack, waterbox, Westcoast Dual 38 intake, Dual SBN 38s, 440 pump and a 16.5 degree SS Skat imp. Lightend flywheel"
    97' Tigershark Monte Carlo 1000 fresh top end and runs finally!

  2. #2
    Frequent Poster JustStandups's Avatar
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    Re: Base settings on A dual 38 set up.

    All my pjs 550 motors came stock with dual 38 keihins and P 78, main at 100. You may want to bump it up a little since your ported.

    Sent from my SAMSUNG-SM-G870A using Tapatalk
    VHP7000 #132 T1
    VHP7000 #169 T3
    VHP7000 #174 project PJS Triple 795cc
    550sx PJS all over w/ 440 fully ported

  3. #3
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Base settings on A dual 38 set up.

    IMO, that cylinder and pipe would have better chances of being reliable,
    if it had a 440 pump instead.

    That is how 550 mods were raced.

    I am reluctant to issue an estimate. There are too many variables that will
    affect the jetting.

    If your ski was set-up like the VHP, his estimate would be close. But you need
    richer jetting when your pump, engine, and pipe are not well matched. There are
    other factors too. Makes it difficult to estimate specs.

    Dual 38 BN's would be easier, but a 440 pump would be better.


    Bill M.
    Last edited by wmazz; 03-19-2017 at 11:39 PM.
    Horsepower == Speed, RPM != Speed



  4. #4
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    Re: Base settings on A dual 38 set up.

    so 90 low and 110 high? be good numbers?

    I dont know what the psi will be on motor i think i have 19-21cc domes on head. so a guestamate is 195-205. Its a Full Wescost exhast I might shorten pipe for better top end. its a 550 pump with a 16.5 pitch imp.

    Bill: Only looking for an estimate so i dont blow up the motor on the first outing. id rather run rich then lean.

    Also where can i get carb jetting online cheap?
    Last edited by stixx925; 03-20-2017 at 01:18 AM.
    90' 550SX "Shaved head, .5mm+ Wiseco pistons, SBN 44, Kerker exhaust, Mariner waterbox, WestCoast OS Gas Tank, extended ride plate,(440 pump) 16deg SS Skat imp."
    WIP - 83' JS550 " .5mm+ Wiseco pistons, WestCoast: Head, rc520 reed cyl, 7 Ring Exhaust, Ext Ride plate, Ex Manifold, 2x Velocity stack, waterbox, Westcoast Dual 38 intake, Dual SBN 38s, 440 pump and a 16.5 degree SS Skat imp. Lightend flywheel"
    97' Tigershark Monte Carlo 1000 fresh top end and runs finally!

  5. #5
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Base settings on A dual 38 set up.

    Quote Originally Posted by stixx925 View Post
    Its a Full Westcost exhaust I might shorten pipe for better top end. its a 550 pump with a 16.5 pitch imp.
    The 550 pump works like a rev-limiter. So you could shorten the pipe for better
    top end (at a higher rpm), but the engine will never rev with the 550 pump on it.

    That is why the 550 comes with a rev limiter and the 440 does not. The 550 pump
    loads the engine down, and when it unloads, the engine will easily rev to +10,000
    rpm. The 550 is equipped with an electronic & mechanical rev-limiter to prevent
    the connecting rods from snapping in half when the pump catches air, and the rider
    didn't let off the throttle.

    (please don't confuse the actual rev limiter with my analogy that the 550 pumps
    acts like a rev limiter. They are 2 different concepts)

    When a pump holds the engine rpm to a lower rpm than where the engine creates
    peak HP, the load creates a lot of heat and increases the possibility of detonation.

    550 pumps like long pipes, that make peak hp from 6500 to ~7000 rpm. The 550
    limited pipe (half pipe) is an excellent example of a good pipe for 550 pumps.

    If your Westcoast 550 reed cylinder is ported with a high compression head, it will
    have less torque. A compromise would be a 15' impeller, bored nozzle, and a Coffman
    440/550 pipe.

    The 550 pump is a great pump, but not a great race pump. A few people did race
    with 550 pumps, but it took a special set-up to do it.

    Your reed cylinder, half pipe, single 38 or dual carbs, pump and impeller with a bored
    nozzle would be a fun ski.


    Bill M.

    It is very important that your engine, pipe, and pump are matched, to allow the
    engine to reach or slightly exceed peak HP rpm in the water.
    Last edited by wmazz; 03-20-2017 at 11:07 AM.
    Horsepower == Speed, RPM != Speed



  6. #6
    Top Dog bandit88's Avatar
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    Re: Base settings on A dual 38 set up.

    I agree with Bill, that motor wants to rev and needs a 440 pump. a 750 pump conversion should work nicely as well.
    -95 750SXI
    -86 440 undergoing PJS800 conversion
    -90 TS650

  7. #7
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: Base settings on A dual 38 set up.

    im running a ported reed kawi engine on 100 octane with dual sbns. ive run both a 440 pump and a 550 pump on the same engine with the same pipe. the pipe is a factory full pipe, the chamber length is slightly longer than the west coast pipe. i saw you're running a 550 pump with a straight 16. the port timing is lower on my reed engine than your rc cylinder. im running an 11/16 with a 70mm nozzle and a stubby cone and i could use less impeller i think. run the largest outlet nozzle you can find as well. A half pipe would be better for the 550 pump too. bill is right about the 440 pump with the rc cylinder. before i had the reed engine built and ported, i had a pjs viper cylinder and the 440 pump. ran solid. i also switched from dual keihins to dual sbn 38s. I would highly recommend the 440 pump setup with that cylinder. the guy i bought the engine from was running a 550 pump with a 15/20 and it was fairly sluggish. also you will want to run that pipe pretty dry so it gets hot enough to turn the rpms. its aluminum and doesnt hold heat very long.

    for carb settings i would start with a 70-75pilot, 130high and tune down from there. 65g spring and 2.0 popoff should work depending on your port timing. im running 75 low 125 highs. youll need more fuel on the highs for more rpm.

    newmiller also did my engine. ask him, will tell you what to run after he looks at your cylinder. he knows his engine and tuning chit pretty well.
    Last edited by fastgtfairlane; 03-20-2017 at 07:34 PM.
    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
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    Re: Base settings on A dual 38 set up.

    that's another chunk of dough i don't wanna spend but it makes since, i need a cheap cheap 440 pump. what pitch imp.
    90' 550SX "Shaved head, .5mm+ Wiseco pistons, SBN 44, Kerker exhaust, Mariner waterbox, WestCoast OS Gas Tank, extended ride plate,(440 pump) 16deg SS Skat imp."
    WIP - 83' JS550 " .5mm+ Wiseco pistons, WestCoast: Head, rc520 reed cyl, 7 Ring Exhaust, Ext Ride plate, Ex Manifold, 2x Velocity stack, waterbox, Westcoast Dual 38 intake, Dual SBN 38s, 440 pump and a 16.5 degree SS Skat imp. Lightend flywheel"
    97' Tigershark Monte Carlo 1000 fresh top end and runs finally!

  9. #9
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: Base settings on A dual 38 set up.

    440 pump stuff is usually pretty inexpensive. unless you want an afterburner pump. not really do much more than a good extrude honed 440 pump. depending on your outlet nozzle diameter, between 15.5 to 17 would be ideal.
    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

  10. #10
    Top Dog
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    Re: Base settings on A dual 38 set up.

    Any one know where I can g3t cheap jetting for the 38s? Thing is its 4.50 per jet at ski shop. Online it's 1.75 +6.95 shipping. I just wanna order several jets so I can fine tune carbs.
    Last edited by stixx925; 03-25-2017 at 01:32 AM.
    90' 550SX "Shaved head, .5mm+ Wiseco pistons, SBN 44, Kerker exhaust, Mariner waterbox, WestCoast OS Gas Tank, extended ride plate,(440 pump) 16deg SS Skat imp."
    WIP - 83' JS550 " .5mm+ Wiseco pistons, WestCoast: Head, rc520 reed cyl, 7 Ring Exhaust, Ext Ride plate, Ex Manifold, 2x Velocity stack, waterbox, Westcoast Dual 38 intake, Dual SBN 38s, 440 pump and a 16.5 degree SS Skat imp. Lightend flywheel"
    97' Tigershark Monte Carlo 1000 fresh top end and runs finally!

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