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  1. #1

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    92 650 conv to 780 HELP

    O.k here we go again!!! I am trying to get my ski going again this year i started this project last year and had some bad luck with it!!! To start with i want to double check what my piston clearance and ring gap should be? I am using wsm piston kit and i am bored to the max 1mm over. Also i want to see what every body thanks my jetting should be? my set up so far is a 92 sl650 with newly bored 1mm over 780 cylinders ,ocean pro aftermarket flame arrester, boysen reeds with the 780 reed spacers, i installed all the stock components(jets,pop off,etc) for a 780 in my carbs last year, and the 92 650 pipe with a aftermarket water box.


  2. #2
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    I would recommend going w/ the 97 780 jetting specs. They had the largest mains of any other yr.I would also recommend that you open the high adjusters a bit more than spec for 97 780 because of your over bore. You will still need to read the wash till you know its right.

    97 slt and sl780= mag 125 cen 122.5 and pto 130 w/ 70 pilots.
    96 slx 107.5 and 72.5 pilots or 110 and 67.5

  3. #3
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Ring gaps .012 to .020. Cyl clearance .003 to .005 w/ wear limit at .008

    It's all in the manual here.

  4. #4

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    Thanks starflight!! Anyone have any other suggestions?

  5. #5
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    You're welcome!
    Who did the boring? Is he used to doing 2 stroke work? Did he re-chamfer the ports?

  6. #6

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    My brother did the work!! yelp we re-chamferd the ports!! thanks for lookn out for me !!!

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Keep the 92 650 CDI installed, it's a good timing curve.

    The dry pipe is going to affect jetting.

    I was going to suggest the G/F's jetting, but hers is a 750. Very different fuel requirements. (MAG 127.5 CEN 122.5 PTO 127.5 with lows at 87.5)

    When I was running that similar set up, I had the 44mm carbs, so jetting wouldn't even be close. (not to mention it didn't stay this set up for long)

    This is just a wild guess, but maybe start around a 125 main with a 75 low. Unfortunately this is a custom set up, so no book is going to have anything to follow. You're kinda on your own, with the help we can offer here.

  8. #8

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    Thanks guys!!!

  9. #9

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    i got a 110 for a main and 67.5 for low you thanks that is to small?

  10. #10
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    I'm thinking you'll need to go bigger on both. I'd rather start on the fat side and work my way back, but you can give it a shot. Just keep a close eye on the piston wash pattern. Check this out...

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