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Thread: 96 Wave Venture

  1. #1

    Unhappy 96 Wave Venture

    I bought a ski last year, a 1996 Yamaha Wave Venture 700 to be specific. Anyways, it ran a little rough when I first got it, and after about 2 hours of use, it was horrible. I took off the head, and lo and behold, the rear piston had completely lost the compression ring along with about an inch of the ring land (chipped off the top of the piston, 1" by maybe 1/8" piece). Apparently, both pieces had been jettisoned through the exhaust, as neither were in the top or bottom end. Suffice to say, a rebuild was in order.

    While I am not an expert with 2-stroke engines, I have a good idea of how engines work in general, and I completed the rebuild with the help of a factory service manual. Upon taking it out to the water for break-in, the ski ran good--not great, but good, much better than when the piston was broken.

    After the first session of break-in, I take the ski in to cool down. Upon firing up for the second session, the idle is a little rough. The idle gets worse as the sessions go on. While the ski is broken in, I am not sure of the issue at hand.

    I have not been able to verify compression (the cylinders were within spec at rebuild, both pistons, rings, wrist pins & needle bearings, and all gaskets were replaced). The high and low speed settings on the carbs were set to factory defaults, and for the first tank of gas, oil was added (if I remember correctly, I did a 50:1 pre-mix, in addition to the oil injection system).

    When the ski ran, it would run flawlessly up top (beyond about 5-8 mph), however the bottom end of the rev range wasn't as great. To start the ski, you had to give it full choke and a little throttle while pressing the starter button. When the ski cranked, you had to hold the throttle until it could power out of the low speed at which point, it just took off at about 8 mph. Beyond there, throttle response was crisp and no real hesitation was apparent. If you tried to give any throttle from the bottom end, it would just bog down and die. When warm, the ski would sometimes idle fine, but again, any throttle input would cause it to die.

    Another thing I noticed. After running at high speed for a few seconds (25+ mph), the ski would randomly lose power and shut off, like the fuel was being cut off.

    My question is... where should I start?

    I will check the compression as soon as I can get my hands on a tester, but my hopes are that it is either ignition or fuel related.

    BTW, the ski is not completely broken in. It has about 1.5-2 hours on the rebuilt engine. According to the "Proper Engine Break-in Procedures for Jet Skis" available at a few different places on the web, I was at the point where I could go 90% throttle (3 sessions of 30 minutes each, plus idle time).

    Any ideas?

    edit:

    For reference, the rear piston mentioned:
    Last edited by Daqq; 01-23-2009 at 11:29 PM. Reason: Add picture of original rear piston


  2. #2
    you never touched the carbs? or did i miss the carb rebuild ?

  3. #3
    PS Welcome to the site! We may smack you around a little at first .. but we will get u dialed in

  4. #4
    Moderator DrewNJ's Avatar
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    I'm with ZMANN on this one...
    The part of your description that scares me the most is:

    "Another thing I noticed. After running at high speed for a few seconds (25+ mph), the ski would randomly lose power and shut off, like the fuel was being cut off."

    This is usually an indication of seizing...

  5. #5
    Right u Drew are and that old piston has lean written all over it , not sure why it snagged a ring ? maybe wear and to much clearance and maybe a seizure helped it catch

  6. #6
    Tlhe carbs were not rebuilt.

    Should this be my first course of action?

    I can pop the head back off and take a look at the cylinder walls if need be, even if it means a new head gasket (I know in a 4-stroke world it does).

    As far as I'm aware, the oil injection system pumps in a certain amount of oil based on engine rpm, not fuel settings, am I correct? In this case, even when lean, the engine should still be getting a proper amount of oil (but I understand a lean condition is not good for the engine).

    Should I check the oil injection system instead?

  7. #7
    Quote Originally Posted by Daqq View Post
    Tlhe carbs were not rebuilt.

    Should this be my first course of action?

    I can pop the head back off and take a look at the cylinder walls if need be, even if it means a new head gasket (I know in a 4-stroke world it does).

    As far as I'm aware, the oil injection system pumps in a certain amount of oil based on engine rpm, not fuel settings, am I correct? In this case, even when lean, the engine should still be getting a proper amount of oil (but I understand a lean condition is not good for the engine).

    Should I check the oil injection system instead?
    2 strokes really depend on the proper fuel ratio , and most engine issues are fuel related , if your mechanically inclined .. and u are the carbs simplicity will impress u! don't pull the head but a compression check is always good and you can usually inspect the pistons thru the plug hole using a led light ,, when u are ready for carb kits and rebuild instructions let me know

  8. #8
    Moderator DrewNJ's Avatar
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    The first thing I'd do is check compression. If you don't have a gauge then either pick up an inexpensive one or rent/borrow one.
    Others may give you/me crap but I've had good luck with the $20 one at wal-mart..
    If both cylinders are fairly close then your probably ok, then pull the head if you want... If you remove the head you can reuse the gasket as long as it's in good shape.

    If everything checks out ok then pick up 2 carb rebuild kits and some new needles/seats and rebuild the carbs. If you didn't take a good look at the reeds when you had the motor apart it would be a good idea to take a look at them when you have the carbs off.
    Good Luck
    Doug

  9. #9
    Quote Originally Posted by Daqq View Post
    Tlhe carbs were not rebuilt.

    Should this be my first course of action?YES


    Should I check the oil injection system instead? I would suggest premix on this craft
    the 700 uses a fixed rate pump unlike the 1200's variable rate , however the pumps are rarely the issue it's the 10 or so connections and check valves that seem to fail

  10. #10
    Will take a look at it all tomorrow and I'll report back once I have any updates. Thanks so much, guys.

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