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  1. #1
    cheatin' piston popper addicted's Avatar
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    My jetting-SL 750

    Since my ski seems to disregard all commonly held knowledge, I figured I'd post my jetting and set up. When I installed flame arrestors, Most said that all I needed to do was open the needles 1/2-1 turn more than stock. That didn't work for me.

    Maybe it will help someone not blow up there motor this holiday weekend.

    94 sl750
    +1mm sbt jugs and pistons
    Stock carbs
    pentagon triple fuel pump
    reed spacer
    boyesen pro reeds
    tau ceti F/A's
    stock compression
    87 octane
    injected with Amsoil HP injector, non variable pump.
    650ft ASL


    Stock was
    75P
    90M
    18pop

    I had no wash and melted a piston!

    I was at:

    80P 1/2 turn
    110M 2+ turns
    18pop

    until I checked wash last night. Mid and rear cylinders just have a pinky nail sized wash on some ports, MAG had a tiny, tiny bit of wash on 1 port.

    I re jetted last night to:

    80P
    115M
    18pop

    My low speed is fine. Idles cleanly and accelerated hard at 1/2 turn out. with the stock pilot jet I was at 2 1/4 out. I am hoping that the 115's are too big, and that I will be more than safe when the cold weather arrives, even If I need to keep the HS needle closed in the summer.

    Maybe I ended up with some kind of ported cylinders from SBT? I don't know, but the F/As yielded alot of RPM's for me, but it needed a whole lot more gas. Also, the plugs looked rich the whole time

    Moral of the story. . . Don't believe your plugs, believe your wash, and give that thing as much gas as it needs. Jets are cheaper than pistons.


  2. #2
    ph2ocraft's Avatar
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    AMEN!! Piston wash works for me. Have you checked tuning on the ground strap(for lack of better term)?
    Did you by any chance see what your fuel pressure was before the restictor? I'm curious as I'm thinking if the pressure is low maybe we wind up with tuning issues. This is just a guess on my part but I'm going to check it out next week. I think the magic number is supposed to be 6 pounds or tuning issues arise? I know this works for the Novi set up and it may not even apply in this case nor the Keihins but I want to play with it just the same.

  3. #3
    race24x's Avatar
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    Hi there sorry to kind of jack your thread but how do you check piston wash and what am I looking for? I did a search but only came up with a tool to look inside.

  4. #4
    Moderator beerdart's Avatar
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    Quote Originally Posted by race24x View Post
    Hi there sorry to kind of jack your thread but how do you check piston wash and what am I looking for? I did a search but only came up with a tool to look inside.
    Go here Ph2ocraft Gallery and click on tech section

  5. #5
    race24x's Avatar
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    Thank you he had a great article there. I always used the old check the plugs after running it hard method.

  6. #6
    cheatin' piston popper addicted's Avatar
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    Quote Originally Posted by ph2ocraft View Post
    AMEN!! Piston wash works for me. Have you checked tuning on the ground strap(for lack of better term)? HUH?? Please explain
    Did you by any chance see what your fuel pressure was before the restictor? I'm curious as I'm thinking if the pressure is low maybe we wind up with tuning issues. This is just a guess on my part but I'm going to check it out next week. I think the magic number is supposed to be 6 pounds or tuning issues arise? I know this works for the Novi set up and it may not even apply in this case nor the Keihins but I want to play with it just the same.
    I did not check fuel pressure, but I can tell you that the pentagon pump has alot more pressure than the round pump. On the old pump I was running the popoff around 12, now anything less than 18 will dribble.
    Last edited by addicted; 06-29-2007 at 01:07 PM.

  7. #7
    cheatin' piston popper addicted's Avatar
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    race24x,

    Check out this thread too.

    http://www.greenhulk.net/forums/show...ht=piston+wash

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    You always know when I'm about to PM you Addicted. I was looking for your carb adjustments again. 94 SL 650/750 conversion .25mm OverSize. I too added the reed spacers, V Force II reeds, and Vortex F/A's. 70 lows (going to go bigger on lows with premix)100 mains were still too lean. Jumped to 112.5 (that's what I had on hand) and was coming up with too rich. I think I'm looking at 105 to 110 mains. But, stupid me had to replace the crank seals, so I just threw in the PSI dry pipe and a 12/18 impeller instead of the 13/18. I'm gonna see what happens with that pipe and screw before I change the jets. I'm hoping it will require a little more fuel and be perfect were she's at. Hey Addicted, any chance of me getting that speed sensor you offered up? Thanks

  9. #9
    cheatin' piston popper addicted's Avatar
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    X, 75 lows are stock for a 750. I would raise those up ASAP. As I understand it, you want to jet the carbs so that the needles are right around 1 turn out. With the dry pipe and added rpm's, you probably want to go way up on the jetting to be safe. you are going by your wash and not the plugs, right?

    PM me your address again and I will try to get the speed sensor pickup out tomorrow or early next week. Work is going to be crazy Monday.

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    I was going by plugs only, until I get close enough to inspect wash. No sense in removing heads when I know I've been lean until last test run with 112.5's. Then my crank seal went bad, now I'm almost ready to try again.

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