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  1. #1

    tuning the carbs 97slt 780

    I decided to take the step and adjust the carbs on my ski even though the guy i bought it from was extremely knowledgeable on the two stroke motor, I felt as if he had dialed the carbs to there maximum potential. When viewing the plugs after riding they where clean as a whistle with a tiny bit of grey splatter on the white electrode not chocolate brown by any means, also running like a bat out of hell just zip zip zip everywhere you go. Of course this was not at a plug chop situation so doesn't mean anything except it's lean at an idle right, so i twisted some knobs"like a knob" and been playing hell trying to get it right.

    I found the specs finally for the turn outs on high and low, noticing that it had three different settings for the high
    M 1 1/8, C7/8, P1 1/4, assuming this is because of technical things such as fuel tank, lines, feed, and setup. SETTINGS ARE FOR 96 SLX 780 Not 97 SLT 780

    Now for the question. can I tune these skis without the air box on so I can get to the screws easier, or does this mess up the air flow which gives me a bad reading and when I put the air box back on will it restrict the air flow and have it all out of whack?

    And can anyone give me any tips on how to smooth the idle out having three carburetors turning an low speed adjustment on one with the motor shaking doesn't help the other two from shaking so how do I listen for the smoothness? Or am i looking at plugs to dial the idle in?

    Also holy crap haves you ever googled chocolate brown...that color can be anything.haha lol. I noticed when dialed in like a race ski the fuel economy was exceptional. after I dialed it back and got yes chocolate brown for sure the fuel economy went way down, burned off 15 gallons in one day real quick. Can i dail it to where it's not a clean plugs but more like tan for fuel economy and be safe.I'm looking for longevity here kids and wife don't desire to go much faster than 35-40 anyway.
    Any input would be great. I think i got the routine down on how to adjust now but any "deadly watch out fors" so i don't kill my ski would be nice. Thanks
    Last edited by Un-cowJ; 05-31-2014 at 10:13 PM. Reason: correction to misinformation

  2. #2
    I like pipes. I love boost Mr. GP1800's Avatar
    Join Date
    Jun 2010
    Milwaukee WI
    If it was running good I would have left it alone and just watched the piston wash.

  3. #3
    johnsonmtz's Avatar
    Join Date
    Oct 2006
    Mt. Zion Illinois
    I don't have a manual in front of me, but if memory serves right, the '97 SLT780 used different sized high jets in each carb and a uniform # of turns on the HS needle. I know for certain my '96 SLT780 has identical HS jets on all 3 carbs and differing turns on the needles, which I think are the values you posted.

    You're best off to do your tuning runs with F/A in place to avoid running lean during testing, then rich wiht the F/A is reinstalled. As Bryan said, wash is better to watch than plug color if you're not going to do WOT plug chops.

  4. #4
    I was doing 3/4 throttle plug chops from what i read, but no WOT plug chops. How long should i ride at WOT before i cut the power? I was running the 3/4 throttle for 2-3 mins then cutting it is this even long enough. In the literature I found it stated 5 mins rides at 1/4 throttle
    for low speed adjustments, a"couple" mins for high speed adjustments at 3/4 throttle. And i just seen the screen shot i took and it is the 96 values. Thanks so much for that catch man. I would've been beating my head against the dock wondering wth.

    Did the piston wash check. Finally figured out how to upload pictures I think. Should the piston top be smooth or casted looking. It's not bad pits but I do notice that one of the triangle stamps in the piston head, the outside edge of the stamp ring is faded a little still exists but a little faint. I haven't leaned any of the screws only counter clock wise turns since purchased and 1/8 min and 3/8 maximum turns on the high speed the center carb opened it as far as the stopper cap would let me and it still needed more. The carbon build up seems to be flaky and not very attached on the outside edges is this recent build up or old burning off you think, or is there any way to even tell.
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    Last edited by Un-cowJ; 06-01-2014 at 10:26 AM.

  5. #5
    I posted pics of the wash on the wrong damn post sorry really fumbling here with this phone.

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