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Thread: Tuning help

  1. #1
    race24x's Avatar
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    Tuning help

    Hey guys I put my motor all back together and initally had some trouble fouling plugs. I put some new BP8ES in it and after I cleaned it out it ran decent. I was still having some issues with top end. On GPS only about 38 MPH. Also had trouble pulling me and my 110 pound GF out of the water straining to plane off. Rode around most of the day OK. At the end of the day it was starting better and not fouling plugs I went to do a final plug chop just me and going across the lake in really smooth conditions it seemed like it hit a burst of power. RPM's increased and GPS was around 43 44MPH. It pulled me out of the water better than it ever has She was dressed and woldnt get back on but I cold tell it was pulling much better. Went out across several times checking it plugs look perfect chocolate brown WOT chops. My buddies all kind of leaned towards electrical maybe something getting wet weak spark or something riding all day dried it out etc. I wish it went that good all the time it was much more fun that way. So can gas level make it feel that much different all day riding made it lower on fuel and lighter? Restricted fuel line or something like that and it cleared out? Should I open up the CDI box and check it for water I did sink it once? Anything you could suggest would be great I will look at it all.

    My Sl 750 has a 92 dry pipe .010 over 100 jets on mag side 95's in other 2 I am running the 92 SL650 CDI box and right now the 92 pump but I am getting the extended pump and power trim so I am hoping for 50's maybe on GPS


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Make sure your plugs have the "R" in the number. It stands for resistor type spark plug. Check your piston wash, maybe you're running too rich on the MAG and effecting performance. Definately open the elec box and inspect for water inside the box.

  3. #3
    race24x's Avatar
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    I didnt think the R was important it was just for a resistor. When we get snowmobile plugs we kind of joke without the resistor the radio wont work right. Is this important for Watercraft?

  4. #4
    You've got a 750 motor and 650 CDI? I suppose depending on years you're alright, but I know when I put a '94 750 motor into my '94 sl650 ski I didn't get any spark. The 750 was listed as having digital ignition. Swapped it out with a matching 750 CDI and had spark. I know your's runs, but maybe there's some sort of disagreement in there that could be giving you weak spark.
    Last edited by mystahagy; 08-14-2007 at 10:19 AM.

  5. #5
    race24x's Avatar
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    That could be too but even the wire colrs where the same I had to change 2 ends on 2 wires to fit into the 650 box and I think it was Xlint that checked the ignition timing and the early 650 and later 750s had similar timing

  6. #6
    Yeah when I swapped CDI's it was a direct replacement, every color matched up. Difference was, this one worked. Yours is probably fine then, just thinking out loud.

    BTW just for grins, what year is your motor, and if you've got the box open what's the ID# printed on your CDI? My shop manual has the table of CDI's and corresponding motors, wanted to have a looksee. It sure got me lined out.

  7. #7
    axgrider73's Avatar
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    Quote Originally Posted by race24x View Post
    I didnt think the R was important it was just for a resistor. When we get snowmobile plugs we kind of joke without the resistor the radio wont work right. Is this important for Watercraft?
    Yes, it is very important. Without the resistor plugs the ignition will cause RFI and disrupt the micro-processing within the CDI causing misfires.

  8. #8
    race24x's Avatar
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    Man this thing is fickle. Good news is that it is running OK plugs look a little dark but very good not light brown a little darker almost bark colored but better a tiny bit rich than lean right. It just seems like it runs really good once in a while. Most of the day riding it struggled to get me and my GF out of the water but took it out today and it pulled my daughter and I right out in fact I took her friend too. Sometimes it runs 37- 38 and others 43-44 and yes you can tell when its running good it turns up more and pulls harder. I tried messing with the slector switch but no difference and the plugs look very good I dont know if I would blame jetting at all. Any other ideas. If the CDi is the culprit I would think it wouldnt even run.

  9. #9
    Moderator beerdart's Avatar
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    How is the Jet Pump??

  10. #10
    race24x's Avatar
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    I am getting one from Polaris nut in nice shape long pump with trim but right now mine is a POS original 92 stator is a little rough impeller looks OK but didint check clearance between wear ring and impeller. Do you think this can cause some of the issue?

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