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  1. #1

    cant get 7300 RPM after carb rebuild

    hello all,


    1999 kawsaki 1100 stx


    I just replaced my shaft bearing/seals and rebuilt my carbs while at it. all was well with the shaft/bearing.

    However I can't get more than 6400 rpm, 7300 is normal. thus my top end is only 45 mph. I also lost my "snap" acceleration. it does not skip or miss.

    when I first took it on a drive test not only could I only get 6400 rpm, but it slowly bogged down on and shut off. restarted immediatly but then only got about 3500 rpm. filled it up with gas and it drove up to a steady 6400 rpm, no more bogging down and cutting off. and some of the 'snap" acceleration came back. but still no more than 6400 rpm.

    I feel it is a fuel releated issue. espicially since the problem changed after putting fuel in the gas tank. As I mentioned I pulled the engine and rebuilt the carbs. I also replaced my cracked gas cap.at the same time so I thought perhaps the cracked gas cap was masking a fuel vent problem. So while drive testing it I lossened the cap. the issue is still there. the problem is there on reserve and on normal fuel selector.

    i did not do a pop off test after rebuilding the carbs, i bought carb kits from SBT. the needle seat travel was about the same as before.

    any help is appriciated

    Wax man


  2. #2
    Wake junky Gp1200R's Avatar
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    My gpr did the same after building the whole motor. Had like 1 hr on it!!! Turned out being dead cylinder and mine only made 6700 no skipping or missing either. It was only running on two cylinders and resulted in two good cylinders getting so hot they ate away at the nikasil!! So do a compression check..

  3. #3
    steve45's Avatar
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    Did you find any trash in the carbs? How did you clean them? Do the slides move freely? Did you replace the diaphragms? Any trash in the fuel filter? What do the plugs look like?

    "...i bought carb kits from SBT", always a questionable source.

  4. #4
    Wake junky Gp1200R's Avatar
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    Speaking of that I had a paper towel lodged in my exhaust manifold so be sure to check it out..

    Nate

  5. #5
    ok, here is what I have done and observered so far

    compression test 90-110-115

    the sliders in the carbs move good when snaping the gas, except for the cylinder with the 90 psi

    I took apart the carb, inspected the rubber gasket for that slider, no rips, sits nice in the carb and cover fits over nice

    am I looking at pulling the motor apart? bad reed valve? as I said i never took the motor apart, only to replace the shaft seal.

    thanks

    Wax Man

  6. #6
    I forgot to mention that the one slider that does not move when snaping the gas does move good and smooth with my finger withthe engine off,

  7. #7
    steve45's Avatar
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    You have a low cylinder.

  8. #8
    Quote Originally Posted by steve45 View Post
    You have a low cylinder.
    Understood.

    Would that low cylinder cause my slider to not open?

    I will take apart the motor and inspect the low cylinder. While I am at it I think I should re-ring the good cylinders while at it. Should I give them a quick honing? Do I need the Kawa ring compressor or can I use a generic ring compressor?

    thanks
    Wax

  9. #9
    steve45's Avatar
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    Hone all of them. New pistons & rings in all of them. The slide operates on differential pressure, a function of air flow. I suspect a low cylinder could keep it from opening properly.

    Buy good parts.

  10. #10
    Quote Originally Posted by steve45 View Post
    Hone all of them. New pistons & rings in all of them. The slide operates on differential pressure, a function of air flow. I suspect a low cylinder could keep it from opening properly.

    Buy good parts.
    ok so I dissasembled the engine, 2 of the 3 cyclinders are fine but I will hone and replaced pistons and rings.
    The low cyclinder (90 lbs) clearly has a bad spiston, there is some minor scoring on the cyclinder wall. after honing that cylinder I really cant feel the scoring anymore. My thoughts (and hopes) is that with a new standard piston/rings should be ok.

    thoughts and opinions on that? all parts are OEM btw

    Also can I use heat to remove the wrist pins? what about putting the pins back in? any suggestions about comprseeing the rings back into the cylinder?

    thanks
    Wax Man

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