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  1. #1

    1996 slt780 throttle ?

    Have a question need help. just rebuilt PTO cylinder and broke it in over the last couple weeks. runs good but the only thing is as I give it gas it runs good to 3/4 throttle but when I give it full throttle it doesn't go an faster

    it doesn't bog, shut off or anything it runs good it just acts like it's not getting any more gas

    the only thing I did with the carbs was richen them up

    the piston wash looked like it was running lean. could this have made it act like that?

    and does have new fuel lines and filter
    thanks in advance


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Carburetors have not been internally cleaned and rebuilt?

    Break-in involves full power cycles. Sounds like you don't have full power, so the ring sealing may be a little less than optimal.

    Get the carbs cleaned and adjusted correctly and go from there.

  3. #3
    BlueFishCrisis's Avatar
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    Quote Originally Posted by Coltsfan View Post
    Have a question need help. just rebuilt PTO cylinder and broke it in over the last couple weeks. runs good but the only thing is as I give it gas it runs good to 3/4 throttle but when I give it full throttle it doesn't go an faster

    it doesn't bog, shut off or anything it runs good it just acts like it's not getting any more gas

    the only thing I did with the carbs was richen them up

    the piston wash looked like it was running lean. could this have made it act like that?

    and does have new fuel lines and filter
    thanks in advance
    I just had a similar issue.... would not change in speed or tone from 3/4 to full. My motor was running rich. Leaned it up quite a bit and running well now..... Not saying that will fix yours, but sounds similar... Still have to watch your wash though.....

  4. #4
    bowsniper's Avatar
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    Check the compression with a good gauge. What did the piston wash look like exactly when it was supposedly lean? all black pistons, or nicks of clean spots, or big fingernail spots ,or blotchy big clean spots? Did they all look the same on each cylinder? Any pictures of it?. Are the jets stock? Do you know the numbers on the pilot and main jets?

    What top speed numbers are you getting on the MFD gauge? The top wot RPMS? That can tell you how far off you are.

  5. #5
    the compression is 125 across all cylinders and the pistons were all black across the tops and the carbs are stock.When I checked the compression I looked in the cylinders and they looked wet on top could this be from to much fuel like being to rich.Like I said runs good no problem starting just when I go from 3/4 to full throttle no change

  6. #6
    bowsniper's Avatar
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    The compression sounds like its fine from what you said. All black is BAD. They are on the edge of meltdown. They all must be richer than that. Any adjustment with the adjusters will take some time before a "new" wash will develop. It may take a tankful or so to see the new wash. What you could do is scrub the piston tops clean and then you will be able to see the new wash pattern developing.

    I would open them up a 1/4 turn( the high speed adjusters) and see what the rpms are then and see where your at and let the wash develop again on the clean pistons. at least you will know you are in a safe zone...better than you are right now. Not sure on the oily look. You would like to see big fingernail spots on the tops. A carb cleaning like Keith said won't hurt anything and I would do what he says first.

    I don't have a 780 so I don't know what the preferred wash should be on that model. But big fingernail size is safe.

    Maybe a member who has one can better direct you on preferred wash. I don't see anything wrong with a 1/4 turn out on the highs>>>>richer . Maybe a 1/8th would be better to get the best rpms but start fat and work your way back up as the wash allows.

    I would not run it until you clean the carbs and fatten it up. would hate to see ya burn a piston..

    What kind of 2-stroke oil are you using and what ratio are you running? What kind of gas? 87 with ethanol?

  7. #7
    guess just can't figure out why it's only from 3/4 to full throttle and everything else is fine and thats what I did I richened it up and now don't have full throttle wonder if went to far?

  8. #8
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    What maximum RPM are you seeing?

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    1. Are your carbs in sync?

    2. Are your throttle plates opening up all the way?

    3. Are you using premix? If so, what ratio?

  10. #10
    yes carbs in sync ,yea and checked the plates opening fully not using premix oil injection

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