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  1. #1

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    1995 SL750 weird engine power loss and die

    I was out for a ride this morning with my son, and about 5 minutes in the motor started to lose power gradually, and then die about 10-15 seconds later. It wasn't like a cylinder was cutting out. It was almost as if battery power was dieing. It would take about 10 or 15 tries to get it to start again, and it would turn over at about 100 rpm instead of the usual 200 rpm.

    Could this be a failing battery? The current one is about 5 years old and I wonder if its now draining during use than the stator can recharge it. Just wondering the best way to trouble shoot this.


  2. #2

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    Also, do the MFD's show numerical error messages? I could have sworn I saw a A56 or A72 or A52 maybe on it just before starting it.

  3. #3
    BlueFishCrisis's Avatar
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    The MFD typical to your ski does not report numerical error messages. The best way to trouble shoot the battery is to simply replace it with a sealed pre filled pre charged AGM style battery. Good first place to start.

  4. #4

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    Quote Originally Posted by BlueFishCrisis View Post
    The MFD typical to your ski does not report numerical error messages. The best way to trouble shoot the battery is to simply replace it with a sealed pre filled pre charged AGM style battery. Good first place to start.
    Are these likely symptoms of a failing battery?

    Since I leave my PWC at the cottage (3 hours away), and I start one last week of summer vacation there next weekend, I can't troubleshoot or repair this week. I'd love to be able to resolve this with as quickly as possible and bring any other likely parts with me as could be required, and within reason!

  5. #5

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    Okay, so I replaced the battery, but still the same (similar) symptom... hard to start and sounds fine at idle and 25% throttle, but any more and it starts to die. I pulled the plugs and the middle and front ones were normal with just a bit of a brown powdery film, but the back plug was black and built-up with carbon... bad!

    I had been idling a fair bit the week before, trying to get my kids up on the skis and wakeboard, so that might have pushed the carbon buildup into the problem region, but I'm guessing that severe difference between this plug and the other two points to another problem. Any ideas what this might be?

  6. #6
    Polarisitis loonatik's Avatar
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    Any maintenance done to fuel system lately?
    Like carb cleaning/rebuild
    Fuel line still in good, clean condition
    Fuel tank clear of build up, debris
    etc,.

  7. #7

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    Quote Originally Posted by loonatik View Post
    Any maintenance done to fuel system lately?
    Like carb cleaning/rebuild
    Fuel line still in good, clean condition
    Fuel tank clear of build up, debris
    etc,.
    I've done no maintenance to the fuel system recently. I do have three carb kits I bought in the spring and am going to use this fall, but otherwise I haven't changed anything since I added the upgraded fuel pump about 6 years ago.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by SeaBee63 View Post
    I was out for a ride this morning with my son, and about 5 minutes in the motor started to lose power gradually, and then die about 10-15 seconds later. It wasn't like a cylinder was cutting out. It was almost as if battery power was dieing. It would take about 10 or 15 tries to get it to start again, and it would turn over at about 100 rpm instead of the usual 200 rpm.

    Could this be a failing battery? The current one is about 5 years old and I wonder if its now draining during use than the stator can recharge it. Just wondering the best way to trouble shoot this.
    Quote Originally Posted by SeaBee63 View Post
    Okay, so I replaced the battery, but still the same (similar) symptom... hard to start and sounds fine at idle and 25% throttle, but any more and it starts to die.

    I pulled the plugs and the middle and front ones were normal with just a bit of a brown powdery film, but the back plug was black and built-up with carbon... bad!

    I had been idling a fair bit the week before, trying to get my kids up on the skis and wakeboard, so that might have pushed the carbon buildup into the problem region, but I'm guessing that severe difference between this plug and the other two points to another problem. Any ideas what this might be?
    Does it still turn over more slowly than it should, prior to actually starting?

    I suspect you may have several problems, not just one.

    Carburetor rebuilds. It seems like now would be a good time. Use genuine Mikuni rebuild kits, not aftermarket. If you bought something else, you can get the correct Mikuni kits from John Zigler.

    Six years since the last fuel system service? You might want to replace the fuel filter at the same time. Again, use an OEM or good quality fuel filter. Must not have a paper filter element. Watcon will have what you need.

    Fuel selector valve may also be contributing to the troubles. Inexpensive to replace at the same time. Rebuilding or replacing the triple outlet fuel pump would complete the fuel system servicing.

    Fresh fuel hoses never hurt. Fuel tank contamination?

    Fresh spark plugs, of the correct type. Genuine NGK only.

    When you do the carb rebuild, be sure to clean the small internal passages. Check and set the arm heights if needed.

    Slow cranking could be several things;

    Remove and clean the engine end of the black battery cable. The blue Fuji engines normally have the engine ground bolt on the bed plate. Sometimes the engine bolts into the bottom of the crank case corrode and create a poor electrical path. You can relocate the negative battery cable to one of the PTO manifold intake studs, or to one of the mounting bolts for the actual starter motor. In all cases, you want clean metal to metal connection between the end of the cable and the engine itself.

    While you are in there, make sure the solenoid ends of the red cables are clean and tight. A bad solenoid can cause slow cranking, as can a corroded connection right at the starter motor.


    Jet pump bearings may be seizing. Best way to tell is to remove the jet pump and inspect. New bearings and seals for the jet pump are not expensive, but you will need to take some tools to get the old ones out and install the new. The freezer and oven method makes it much easier to install the new bearings. Details via my signature links.


    Starter motor or Bendix gear could be binding. With the jet pump and drive shaft removed, see if the engine is still slow to turn over. If yes, try turning it over by hand. Remove the cover from the rear drive shaft coupler. Remove the spark plugs. You should be able to turn the engine over by hand with modest effort. It should turn without any grinding noises or gritty feel. There will be magnetic resistance from the flywheel magnets, but that will feel like a smooth 'cogging' effect.

    If the engine is difficult or near impossible to turn over by hand, then something inside the engine is seizing. Crankcase bearings or possibly the Bendix gear is jammed in the forward engaged position.


    Poor running could also be ignition or electrical. Trim back the spark plug wires about 1/4 inch and re-screw the plug boots on.

    A failing magneto stator or CDI can also cause some of the symptoms you report.


    It is going to take some diagnostics to identify the actual problem cause(s). Do not assume there is only one or even just two problems.

  9. #9
    BlueFishCrisis's Avatar
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    What are your compression numbers?

  10. #10

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    Thanks K447 – those are all great suggestions that I will seriously look at. Right now I'm on my last week of summer vacation with my kids and I'm a single Dad, so I don't want to spend all of it overhauling this PWC. I'll try new plugs, trim back the leads, clean contacts and grease the drive shaft again, but the major stuff will have to wait till fall. I just want to get 7 more days out of it this season!

    Bluefishcrisis – I'll be checking that today. My compression tester was at a neighbours and he was away yesterday.

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