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91 Waverunner 650 ---

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  • 91 Waverunner 650 ---

    recently aquired this toy --- previous owner said it ran great until a few weeks ago. I've read as many threads and posts as possible that pertain to this little quirk we're having.... seems from about 1/2 throttle to wot the rpms don't change!! so far I've disconnected the thermoswitch and ran it, checked all the water lines from the pump to the motor, replaced plugs, set carb to factory specs.... nothing has made a difference. I know this boat isn't a speed demon, but surely should do at least 30-35 mph!! We can barely get this thing to plane and then when you take a hard turn rpm's stay the same but the boat slows to almost a crawl then it takes forever to get back on plane !! Impeller and wear ring both look fair, but I'll be replacing both with good used or oem's... I'm headed out to tear into the exhaust ducts..... compession is good on both cylinders, but I'm starting to lean towards a head gasket, and possible a carb rebuild... I have no way of telling how fast the motor is spinning as I don't have a tach... any thoughts? any ideas? am I on the right track?
    thanks for any and all info

    Dan

  • #2
    Re: 91 Waverunner 650 ---

    I've removed all the exhaust ducting, and the "Bread-box" (heehee)
    seems everything is ok, the bread box was full of water but no apparent leaks in the ducting...

    today we are going to check for air leaks, or vacuum leaks around the intake and carb, maybe try to do a leak down test on the cylinders...

    could the reeds have something to do with it?

    eventually I'll pick up a gasket kit and replace all the gaskets...

    what is the max rpm with stock CDI for the 650?

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    • #3
      Re: 91 Waverunner 650 ---

      think I may have found a contributing factor to the 1/2 throttle quirk... seems someone was already in the carb --- looks like 1/2 a class of 3rd graders tore into it as a class project on "Go home and try again" !!! No internal filter, all the screw heads are booggered, rust and corrosion on the diaphrams, and mounting surfaces, intake was missing 2 bolts, and 3 of 4 gaskets from carb to crankcase weren't sealed!!! Dam...Dam....Dam!!!

      Why can't inexperienced people use the correct tools and the correct parts when installing, or removing things!!!!

      So now I've called all over looking for a carb kit, and gaskets---- not even my local Yamaha dealer has them in stock!! so now we order parts, and play the waiting game... ho hummmm
      Last edited by '91yammyrunner; 06-18-2009, 05:44 PM. Reason: spelling errors

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