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  1. #1

    94 SL 750 carb adjustments

    Newbie to PWC's and Greenhulk, but not new to working on 2 strokes. Bought 2 x 94 SL 750s, blew PTO piston on one right away, disovered Greenhulk and found all the problems this thing had (aways after the fact right?) So far, Upgraded the fuel pump, replaced all gas lines, removed and cleaned out gas tank, cleaned and greased shut off valve, cleaned and installed new Mikuni carb kits, 2.5mm needle and seats (had 2.0's, but I swear I read on here it called for 2.5's..is this ok?), jets are stock #90 High and #75 Low, 18psi pop-off on all 3, installed a new cylinder, gaskets, new piston kit with new cage bearing, performed a vacuum test and indexed crankshaft. THANK YOU GREEN HULK FOR ALL THE INFO. Now, before I attempt to start it, I want to pick the carburetor pro's brains here for a minute. I know the stock jet settings, but this is not 100% stock, Mag cylinder and the Center cylinder have been bored .10 over and the PTO is now .20 over. I've attached a couple pictures of the FA that it has as on it as well. I am thinking of going 1/2 turn past stock on the highs, is that enough or too much in your opinions?... (STOCK High settings Mag 1 1/4, CEN 3/8, PTO 7/ What I'm thinking..MAG 1 7/8, CEN 7/8, PTO 1 3/8. Low's I was thinking of setting at 3/4 instead of 1/4 turn, or do I leave them at stock? Any ideas would be appreciated so I can get this thing dialed in before the snow flys here in MN!

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  2. #2
    BlueFishCrisis's Avatar
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    Go with your intuition on the highs, but I would leave the lows at 1/2. Once you are on the water you can adjust the lows while floating. Do a few plug chops while on the water (hold throttle wide open then pull kill cord). Take a look at the plugs after pulling the cord. Chocolate brown is good, white/gray is lean, dark brown/black and sooty is rich. All this after you go through a normal break in, of course.....

  3. #3
    kaotic1's Avatar
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    Tie the ski to the trailer and run it up adjust the highs until it runs the hardest and then open it up 1/8 turn on all three cyl. this will keep a little extra fuel to it. Now on the lows let it idle on the trailer adjust until it idles best.. then hit the throttle, if it bogs your to lean..open them up 1/8 at a time until it runs up right, this is my method and it works for me on all carb pwcs and outboard motors as well. and weed eaters chainsaws 2 strokes in general good luck

  4. #4
    Quote Originally Posted by BlueFishCrisis View Post
    Go with your intuition on the highs, but I would leave the lows at 1/2. Once you are on the water you can adjust the lows while floating. Do a few plug chops while on the water (hold throttle wide open then pull kill cord). Take a look at the plugs after pulling the cord. Chocolate brown is good, white/gray is lean, dark brown/black and sooty is rich. All this after you go through a normal break in, of course.....
    Thanks BlueFishCrisis. I'll dial the lows in at 1/2 and go with my settings and test the piston wash/plug color after break in and a few plug chops. You don't see a problem with the 2.5mm needle and seats with pop-off coming in at 18? I think it was my mistake ordering the 2.5 vs the 2.0's.

  5. #5
    Kaotic1, I like your idea about tieing it down to the trailer good to get it adjusted..when you say adjust until it runs the hardest, you mean once it's running nice and crisp, not loading up or too lean I assume? I know I'm beating a dead horse here, but are 2.5mm needle and seats going to give me tuning problems? Thanks!

  6. #6
    kaotic1's Avatar
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    Im saying hold the throttle open and adjust until it runs the very best, sounding and feeling you will know when your there...then open them up because that position is going to be lean and cause problems.. good for a short pass but in a long pull will create alot of heat in the combustion chamber, so i open them up an 1/8 to give that little extra fuel to keep it cool. YOU can also do a long pull on open water or the trailer and pull the seat and check the head temps with an infrared thermometer [laser thermometer] or your hand if you cant hold your hand on there its too lean open them up a bit more. Actualy the hand is the best way to tell if things are too hot... 4or 5 seconds on a di, and should be able to keep hand on there on a carb motor.. as far as the 2.5 n&s unless your way oversise on bore I would think this is overkill but i may be wrong maybe k447 will have insight to this

  7. #7
    Perfect, that all makes sense. I set the 2.0's aside in case I need them when I noticed the size difference, they actually didn't look bad but I didn't test them since I was replacing them. Total oversight on my part getting the lrger ones. I'll wait to see what k447 has to say if he sees my post.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    I shall defer to the carburetor experts.

  9. #9
    Polarisitis loonatik's Avatar
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    It does not matter what needle valve size is used, getting correct POP value is all it matters.

    If you don't have correct spring to get POP to right range, you can increase or decrease low jet size to compensate for it. Larger jet for higher POP and smaller jet for lower POP.

    For example:
    Let's say specs calls for 18 psi and 65 low jet and you're getting 24 psi then low jet should be increased to around 75.

  10. #10
    BlueFishCrisis's Avatar
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    No matter what your process, plug chops and wash are your key indicators to prevent a melt down. Check early and often until you are comfortable.

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