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  1. #1

    97 GSX 787 has issues getting to full power

    Hi Everybody,

    I've been slowly working my way through the lack of power troubleshooting section of the service manual, but nothing so far is working and maybe someone here has had a similar experience.

    The machine has good compression, freshly rebuilt carbs, new fuel lines, new ignition coil, rotary valve appears to be in good shape, rave valves were just replaced too. Spark plugs are the textbook brown color of proper combustion.. There was some water damage in the rear electrical box, the so i replaced the connectors going to the coil as well.

    So, on the trailer, the machine revs right up to 7000+ rpm, no problem, however, drop it in the lake and it struggles upto 4000 rpm, and then some times, picks up power again and takes off to full power, usually at which time the speedometer goes dead.

    I have also noticed the trim gauge only displays the lower two bars and will just stay on the second to bottom while it moves up and down through the rest of its range of travel.

    Any one have any ideas?

    Thanks a bunch!


  2. #2
    Check the rectifier.

  3. #3
    flyin' the friendly skies airbornexp's Avatar
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  4. #4
    Quote Originally Posted by Seapoo View Post
    Check the rectifier.
    Charging voltage is normal, I even just tried a new regulator/rectifier, with the same results, had been messing with the high speed screws a lil, went back to the stock 1/2 mag 1 pto setting and it doesn't even plane, just chugs along around 4000 rpms, almost as tho its hitting the rev limiter, and then if you hit a wave, it wwould freespin right up to 7000, but back to 4000 as soon as it grabs again. leaning out the carbs i can get it to plane but am afraid of burning up a piston

  5. #5
    Actually, now reviewing the shop manual and it says high speed screw set 0... That means both? The values i had read before were for an aftermarket flame arrestor and choke, tho i had been just doin the quick tests with the stock flame arrestor and no airbox, which should mean a higher manifold pressure and therefore more air and as such a little richer on the mixture should have been ok? no? It was plaining before tho with the screws all the way in ( i think, pto may have been a lil out tho), but still not achieving full power

  6. #6

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    My book also said set high speed screws to 0 did that blow moter the next weekend. both cyc cook. shop said I did it. when the check over the motor they asked me if anyone worked on the carbs. I said why they told me someone closed the high speed screw to 0. there fore I was not getting enought fuel/oil into the motor. That why it cooked it self. I ask what should it be he said 1/8 but no more then 1/4 of a turn.

  7. #7
    flyin' the friendly skies airbornexp's Avatar
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  8. #8
    Quote Originally Posted by airbornexp View Post

    Great, but that has specs for everything except the 97 gsx, tho the 96 gsx and xp says high speed screw 0, So I guess 0 it is, which is where i had them both last weekend and it still didn't have any power... Should the carbs from my 96 xp work without any adjustment on the 97 gsx? I begining to think the crank maybe twisted

  9. #9
    flyin' the friendly skies airbornexp's Avatar
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    a 787 is a 787 ...isnt it?

  10. #10
    Quote Originally Posted by airbornexp View Post
    a 787 is a 787 ...isnt it?

    I just wasn't sure if there was any differences between the years,
    What about using the 717 carbs on the 787? i think i read some where they were the same size...

    I guess then swapping the carbs from the good machine may be a good step for trouble shootin, But oh what a pain in the rear, 4 more removals and installs gahh. Tho my new stubby 5mm hex drive drive socket from snap-on has made removing the flame arrestor guard a snap.

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