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  1. #1

    HELP! 1992 Waverunner 500 Prob

    Hey all,

    I have 2 Yamaha Waverunner 500s - WR500Q. I seem to be having problems with 1 of them.

    I just had replaced the sparkplugs with new ones (got the ngk recommended on the repair manual). And I've tuned the high speed adjuster to where its making the most punch in acceleration. I tuned it by running at WOT around the lake and killing the engine before going back to base to check plugs. Here's the issue im having: when checking the plugs to see if its rich or lean, one cylinder imo is looking good (closest to front of pwc) and the other seems to me like its running lean (closest to the driver).

    Also, when I was doing the WOT test ride round the lake, it would have great acceleration and then it would slow down a little bit. And it doesn't have the top speed that the other ski has.

    Here's what I've checked/done to troubleshoot so far:

    1. Good spark
    2. Both Cyl is firing.
    3. Switched plugs to see if problem is on the gap of plugs (not that the gap is different)
    4. Switched the plugs around to see if the color changes and it does. one seems to be running lean, and one seems to be getting right AF mixture.
    5. Already checked the carbs and cleaned when I bought it like 2 months ago (was running good).

    What could cause this? What tests can I do to further verify this so I could try and get it fixed?

    I know a leak down test would be a nice one to do for this but I don't know exactly how to do it on the the waverunners since I think I would have to pull the engine out to do a leakdown test cuz it seemed like removing the exhaust manifold to plug the holes is near impossible when i last tried removing it. Really dont know if I could do the leakdown test with the engine still on the hull on the waverunners.

    Help/Advice is greatly appreciated.

    Last edited by bford; 04-26-2013 at 04:50 PM.

  2. #2
    Myself's Avatar
    Join Date
    May 2007
    North Central Arkansas
    Your carb could be all full of trash again. Pull the pickup out of the tank and remove those nasty fuel filters that are probably breaking down and passing the trash to the carb. Use some copper or aluminum tubing to extend the lines inside the tank back to where the filters were. Place a decent filter inline right before the carb. Also check the tiny tubing that runs from the bottom of the engine up to the cylinders, make sure it's not broken. That would cause lean running in one cylinder on the 500.

  3. #3
    Thanks for the reply. I will do all these stuff and will post an update.

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