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  1. #1

    780SL Running issues

    Things done so far
    Carbs cleaned, pop test and rebuild
    Fuel pump rebuild
    fresh tank of 40:1 premix
    Grey wire removed for fuel sender bypass
    Thermostat removed

    So today we managed to get it running but now it won't idle unless if I open up the throttle a little bit. If I let go the throttle the engine will bog down and stall out, restarting the engine takes a few cranks without chokes. Im lost here anyone would know what's causing it to not idle, it idled fine without using the fuel tank, and the fuel lines has a air bubbles.
    Another problem is getting to revv up, with the mfd out Im not sure what rpm I'm running but it seem that it's not running to it's Max rpm, the only way I can get it to rev up a little more if I were to jump on a wake and then the engine will rev up more, there's lots of power but it just dosnt feel like it's operating at it's max rpm. could or be running rich???


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Grey wire is a temporary bypass only. Don't leave it disconnected long term.

    When the carbs were put back together, did you use genuine Mikuni rebuild kits?
    Were the carb screws set correctly?
    Was the idle screw setting on the throttle shaft changed?

    Is the engine actually running on all three cylinders?
    Do they get equally warm?

    Correct spark plugs installed?

  3. #3
    Q. When the carbs were put back together, did you use genuine Mikuni rebuild kits?
    A. unfortunately they aren't mikuni they are Winderosa

    Q.Were the carb screws set correctly?
    A.
    Carb were set to the following settings
    High Speed
    Mag= 1 1/8 + 1/8 for premix
    Center= 7/8 + 1/8 for premix
    PTO= 1 1/4 + 1/8 for premix

    info was obtained Here Scroll to last post


    Q. Was the idle screw setting on the throttle shaft changed?
    A. LOW SCREW 1 3/8 + 1/8 for premix "edit*"

    Info was obtain Here Scroll to last post

    Q. Is the engine actually running on all three cylinders?
    A. Spark on all 3, fire on all 3
    checked VIA removing fuel line and pouring fuel on each carburator and starting.

    Q.Do they get equally warm?
    A. All 3 cylinder temp are equally warm checked by hand not by thermometer unfortunately (didnt think of it ) Thermostat was removed!

    Q.Correct spark plugs installed?
    A.Yes NGK BPR9ES to be exect 1 Year old plugs that has been sitting in the engine but never been used until now still clean!!!

    Curious, why is disconnecting the grey wire must be temporary? Will it effect the machine electronically?

  4. #4

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    I'm new to the hole ski thing but as far as tuning I would think you would set the carbs to factory specs and just add extra oil to the first tank for the break in.. What year is this 780? The settings look like its a 96 but your low speed is set way low for a 96, it should be 1 3/8 out. I don't agree with the extra turns for breakin but again I'm new so I'm also learning, double check your low setting and set them all to stock and see how she runs.. Also the 96-98 780's should be running BPR8ES plugs gapped at 0.024-0.028 in.

  5. #5
    sorry I ment to put 1 3/8 for low jets! The engine is already broken in, we ran 32:1 before and now we switch over to 40:1 I'll check
    the plugs.Its a 1997 780SL

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    The RPM Limiter system is there to warn you about the condition that is triggering the limit. An overheated engine triggers RPM limiting on most models, some also limit on low fuel or low oil.

    With the grey wire disconnected the engine will not limit RPM under any condition. If you don't notice the MFD visual warning right away, engine damage could occur from overheat or lean fuel delivery.

    When fuel gets low it can slosh away from the pickup tube and allow air to be drawn into the fuel lines, starving the carbs for fuel at WOT. RPM limiting for low fuel protects the engine from this situation.

  7. #7
    is there any other ways to bypass the fuel sender???

  8. #8

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    97 ??? carb specs for a 97 are differant than what you are playing with. they are 1 1/4 on low and ONLY 1/8 YES I SAID 1/8 turn on the high!!!! pilot jet is no.70, main jets are MAG no.125 cen no.122.5 and PTO no.130 and the spark plug is BPR8ES

  9. #9
    Your right!! I've been running WAYYYYY too rich!. By the ways why is the setting for and SL different from a SLT and SLX? I mean they have the same engine, right?

    BY SEAOBIN

    SL780 - Low Speed – 5/8
    High Speed – ¾m, 3/4c, 1p

    SLT780 - Low Speed – 1-3/8
    High Speed – 1-1/8m, 7/8c, 1-1/4p

    SLX780 - Low Speed – 1-3/8
    High Speed – 1-1/8m, 7/8c, 1-1/4p
    Thread that i quoted from
    http://www.greenhulk.net/forums/show...nd-piston-wash

  10. #10

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    Quote Originally Posted by Actros617 View Post
    Your right!! I've been running WAYYYYY too rich!. By the ways why is the setting for and SL different from a SLT and SLX? I mean they have the same engine, right?



    Thread that i quoted from
    http://www.greenhulk.net/forums/show...nd-piston-wash
    Well the 1997 SL and the SLT use the Mikuni carbs and have the same setting, the 1997 SLTX uses a Keihin carb.
    As far as the same engine that I don't know but looks like the SL and SLT do but not the SLTX. Let us know how she runs now...

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