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  1. #1

    kawasaki 750 exhaust/low power questions

    Hi, I have just put a rebuilt engine in a 1995 sts 750 ski, and after about 20 hours on it, it runs great but is just missing some power and rpm. Operation is smooth and seamless, up to about 5900 rpm, instead of the 6400 rpm or so I hear it will run. Carbs rebuilt, pop off adjusted, compression about 120psi on both cylinders, just wont get up and go like I think it should.

    Someone mentioned exhaust issues as a possiblity, like something partially blocking the exhaust-Anything on this model in the water box or the rubber connectors that are prone to come loose and block the exhaust? thanks for any ideas before I tear into it.


  2. #2
    u887266's Avatar
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    You are loosing power due to your low compression. A stock 750 will have about 155psi in each cylinder.

  3. #3

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    HI u887266Is right 120 is Way to low 155psi and Yes I also check the exhaust outlets for blockage and also check exhaust leaks that would also do it but your main problem is compression.
    if you need a good machine shop that has parts in stock at a great price I use www.ShortBlocksRus.com they do everything there cylinder boring, Crankshafts, Engines, Performance work ext.

    Good luck

  4. #4
    OK this is an sbt motor still under warranty a they were not too concerned with the compression, although I am not sure why. I also need to try another compression gauge, mine is a harbor freight unit which seems to work fine, thing is I just rebuilt a polaris slt700 as well (sbt crank, wsm top end) and its running about 122 psi per cylinder, also low as well I suspect, except it is running so much faster and stronger than the kawasaki 750 that I am suspicious something else is wrong with the kawasaki. I wrote about that in another thread, but it is a night and day difference between the two ski's.

  5. #5
    u887266's Avatar
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    is the Polaris a 2 cylinder or a 3? If it is a 3 cylinder, then 122psi is ok. Also have you had a chance to brake the 750 engine in yet? Your rings may not have seated in yet, but I can tell you for a fact that 120psi in a 750 is going to give you a loss of power.

  6. #6
    seaobin's Avatar
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    SBT BUILDS THEIR ENGINES TO RUN LOWER PSI SO THEY DONT TANK OUT AS EASILY. FROM WHAT I HEAR, A BRAND SPANKY NEW SBT ENGINE WILL NOT HAVE oem PRESSURE SPECS

  7. #7
    Yes, actually the sbt guys told me they lower the compression a bit on there engines, and yes it has been run about 12 hours or so I would figure its broken in ( the kawasaki) . The Polaris is a 700 domestic 2 cylinder, and no its likely not broken in yet, and the top end was just honed, not bored over, with new pistons and rings from wsm, and even though I am just starting to give it a few seconds of WOT it is so much faster than the kawa I just think something is off on the kawa, even though it runs well, just not fast. Yes some info has come my way from other threads that the Polaris is a faster ski, it just can't make that much difference...thanks for the help.

  8. #8
    u887266's Avatar
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    I dont think that SBT is going to make the compression that much lower. Every SBT engine I have ever got from then, that is 2 650's and 4 750's, all 6 has had 150psi in both cylinder.

  9. #9
    Quote Originally Posted by u887266 View Post
    I dont think that SBT is going to make the compression that much lower. Every SBT engine I have ever got from then, that is 2 650's and 4 750's, all 6 has had 150psi in both cylinder.
    Well, thats good information, I am going to round up another compression tester, mine is new but a harbor freight model (cheap), I dont have any real reason to question the gauge but maybe its off. How soon should full compression be realized on a new engine?

  10. #10
    u887266's Avatar
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    I check my engine after about two hours on the engine and the compression has always been 150psi.

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