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Thread: need your help

  1. #1
    qbzonk's Avatar
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    need your help

    I have been working on getting my boss' '94 650SL up and running. I replaced the entire fuel system (lines, filters, carbs, & fuel pump) and cleaned out the tank.

    It fired right up after the install. I gave it back to my boss and he said it ran great for about 30 minutes, then it fell on it's face. I went out there and even though it fired right up, anything over a cracked throttle would cause it to bog and die.

    I took it back home. Removed the carbs and cleaned them out again. I also replaced the plugs. It took a while to start up, but eventually it fired up. This thing smokes like nothing I have ever seen before. The smoke it predominantly white, but there is also some blue smoke that is typical of a two stroke. On the trailer I can rev the motor full throttle without it bogging down.

    The HS & LS adjusters where set according to the owners manual. Pop-off pressure was about 18-20 psi.

    I do notice that the cylinders get hot very quick compared to my old gp800. There is no hose hook-up for this thing, otherwise I would hose test it and see if the temps come down. Thermostat has also been removed.

    Any ideas as to why this thing is so tempermental? I will be water testing it tomorrow on the lake.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by qbzonk View Post
    ...I replaced the entire fuel system (lines, filters, carbs, & fuel pump) and cleaned out the tank.

    It fired right up after the install. I gave it back to my boss and he said it ran great for about 30 minutes...
    Did you test ride it yourself after the fuel system and carb work?

  3. #3
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    spun the flywheel?

    "sounds to me" like the timing is way off..easy enough to check before things get really bad.

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    It ran good for 30 mins., sounds like you did your job.

    Look for water in the fuel. Some gas caps and filler necks were prone to cracking.

    Take a compression reading, hopefully all is good still.

    If the oil pump linkage is not installed correctly, the oil pump will go "full feed" which may be all the smoke you see.

    You can install a flush kit for running it on the hose. Or, disconnect the 3/4" water cooling hose from the jet pump inside the hull. Adapt your garden hose to it, and run it like that.

    CAUTION: Run engine before turning water on. Then turn the water off before the engine when running on the hose.

  5. #5
    qbzonk's Avatar
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    Quote Originally Posted by nmpeter View Post
    "sounds to me" like the timing is way off..easy enough to check before things get really bad.
    How do I check the timing?

  6. #6
    qbzonk's Avatar
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    Quote Originally Posted by xlint89 View Post
    It ran good for 30 mins., sounds like you did your job.

    Look for water in the fuel. Some gas caps and filler necks were prone to cracking.

    Take a compression reading, hopefully all is good still.

    If the oil pump linkage is not installed correctly, the oil pump will go "full feed" which may be all the smoke you see.

    You can install a flush kit for running it on the hose. Or, disconnect the 3/4" water cooling hose from the jet pump inside the hull. Adapt your garden hose to it, and run it like that.

    CAUTION: Run engine before turning water on. Then turn the water off before the engine when running on the hose.
    Prior to re-installing the tank, I put the cap on the threads and submerged the cap and filler neck hose in a bucket for a few hours and I did not see any water on the inside of the inverted cap.

    I never touched the oil pump linkage, but I can look at it. What exactly am I looking for?

    I'll try that hose mod. I'd feel better hose testing it prior to heading out on the lake.

  7. #7
    qbzonk's Avatar
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    Quote Originally Posted by K447 View Post
    Did you test ride it yourself after the fuel system and carb work?

    Unfortunately not. He's got several skis and a few boats, so I assumed he would be OK. Lesson learned. I will not give this back until I have run a tank or two through it. Then I'll ride it over to his house and have him test it out in front of me.

    I started and stopped the ski quite a bit prior to returning it. It fired right up each time and I was able to rev the engine a few times without it bogging down. All seemed good.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by qbzonk View Post
    How do I check the timing?
    You really should check everything, in case there is more damage than you currently suspect.

    Start with looking at the piston wash, and checking compression.

    Then check crank index.

    Timing is checked using a timing light, at 3000RPM, per the service manual.

    As you now know, you really have to water test a PWC after working on it. Under load on the water, things that cannot be noticed on the trailer can show up. Also, it is hard to properly set the idle without water load on the impeller.

    And of course there can be unexpected water leaks, etc, etc.

  9. #9
    qbzonk's Avatar
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    Took it out today and it ran like crap on the bottom from idle. It fell on it's face before flying at WOT. At WOT it ran like a champ. I could slow to just below plaining speed then hit the gas and be fine. Once I stopped to an idle, it wold die. It ran good for about 30 minutes before it completely went to poop.

    However, when I got it home I pulled the plugs and noticed the mag cylinders plug was ground out with no gap. I think this explains the loss of power after 30 minutes. I was only running on 2 cylinders.

    The weird thing is this is the second time that this cylinder has had the plug gap closed. I will take pics of the plug and post tomorrow. I looked in the cylinder and saw a small scrape, but the plug doesn't have any metal chips in the bottom???? Manual states BR7ES plus which is what I have in it.

    Any ideas?

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by qbzonk View Post
    ...the mag cylinders plug was ground out with no gap. ...this is the second time that this cylinder has had the plug gap closed.

    ...Manual states BR7ES plus which is what I have in it....
    There seems to be some confusion on this question, as other sources recommend the BPR7ES, which has a projected tip.
    Am I getting the Fuji and domestic engines confused?

    There should be no way for anything to mechanically hit the spark plug. Something is going on.

    You may need to pull that cylinder head and check for debris damage. Also check for play in the MAG piston rod end bearings.

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