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  1. #1

    Polaris SL 750 Wont start or rund on 2 cyls but not 3?

    Hi, i've got a Polaris SL 750 3cyl 2 stroke. It will run with two plugs in doesn't matter what cyls? put third plug in and it wont run? I'll take all suggestions....
    it's driving me nuts...


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Runs on any 2 cyls with sparkplugs, but add the 3rd sparkplug and it won't start????

    That is really weird.....

    What's your compression?

  3. #3
    i hadn't run comp test yet, but plan to later today. feel pretty even with just thumb over holes though..
    first thought was plugged exhaust, or low fuel pressure ,it's wierd to me and i have been a auto tech for 27 yrs for Ford. Usually when i see something like this on a car it's due to plugged exhaust...i hear there is alot of good PWC Techs on here? hopefully someone has come across this before..

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    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Wow!!! These engines can run on just 1 cyl (very poorly), or even 2

    Doesn't make sense why adding the 3rd plug would cause it to NOT run... Unless there's a grounding problem?

    The coils are wired in series, so if 1 is grounding out, it will short out the spark to the other 2. Just taking a wild guess here.

    Doubt it's the exh plugged up. The exh manifold ties all together, then flows out the single pipe.

  5. #5
    it's strange i'll agree... ordered shop manual, havn't been able to get any other ideas, but i got nothing but time...it's getting ready to start raining here soon.............. Oregon for ya..

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by xlint89 View Post
    The plugs are wired in series...
    Actually, the ignition coil primaries are in series, but the spark plugs are each on separate high voltage circuits, one plug wire from each coil.

    The ground path for the ignition coil secondaries runs through the primary of the other coils. This makes the diagnostics slightly strange since all coils can affect each other.

    I agree it is a strange problem. Since the three ignition coil primaries are in series, any one of the coils could be causing the problem. Could even be a marginal CDI or stator.

    Which coil is connected directly to the Black wire from the CDI?

    Or it could be a grounding issue. Make very sure every ground in the electrical box, and back to the battery, is a solid zero ohms.

    Disconnect all the black wires from the battery, and separate them. Then measure ohms from the engine block to the electrical box Black terminals. Should be zero ohms.

    My suspicion is that the spark energy is weak overall. Remove all three spark plug caps, and hold all three wire ends about 1/4 inch away from an unpainted part of the engine. You should see bright blue sparks jumping from all three wires simultaneously as the engine cranks.

    In this video, the CDI is a special version with sequential spark. Your Fuji will fire all three spark plugs together, every time. The important thing to note is the strength of the spark, and the color.

  7. #7
    Thanks for the info, i will run those tests and let you know.. it is all orig, probably only has 150hrs on it.. do you suggest alot of upgrades for this model?
    Thanks again..

  8. #8
    OK cut off ends, ran those tests as per video have spark jump about 1/2" bright blue all three wires.... should it be able to jump further than that? also have no other ground wires to batt neg post other than cable itself? i did buy this used with approx 50 hrs only ride it two times a yr or so.. Can you suggest a good place to purchase a complete shop manual ? Talked to People i purchased from yrs ago, said it had been in shop several times in the first yr with starting issues? is this common problem with these? Own alot of banshee twin atv and never had starting issues cant be all that much diff id assume? wondering if i should add more chassis grounds? also would the start switch be a possible concern, for no spark at times?

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by ifixem View Post
    OK cut off ends, ran those tests as per video have spark jump about 1/2" bright blue all three wires.... should it be able to jump further than that?

    ...would the start switch be a possible concern, for no spark at times?
    What year is your SL 750?

    Start switch simply cranks the engine. The magneto then powers up the CDI to run the engine.

    Sounds like you have strong enough spark. It should be a bright blue spark, not yellow.

  10. #10
    its a 95, spark is bright blue after i cut little off the ends of wires, just didnt know how far spark jump video says about a inch and i get about 1/2". out of each. actually i guess i meant to say ign switch up on the handle bar...do you see alot of problems with them? big question is should i be mixing my own oil/fuel mix
    do these have alot of oil injection problems dont know if i should trust it? what ratio do you suggest its all stock..
    Last edited by ifixem; 08-13-2010 at 02:45 PM. Reason: left out words

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