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  1. #1
    qbzonk's Avatar
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    Some questions.......

    I just got this '94 650SL running after replacing pretty much the entire fuel system. I replaced the following:
    - fuel pump
    - tank pick-up
    - all fuel lines
    - carbs
    - N&S
    - plugs

    It ran great at my house. I took it to the lake and it ran great for about 15 minutes. Then it bogged down and refused to run at anything just past idle.

    I went out today and it ran like crap. I replaced the plugs. It ran great for about 30 seconds while I rode it. Then it bogged down and that was it.

    Here are some pics of the plugs that I had in for maybe 10 minutes. The Mag and Center cylinder heads were very hot, but it was very sunny out and anything metal outside was hot to the touch.

    The other pics are of the return fuel line restrictor I put in about 1" past the return nipple from the carbs. It's the only thing I could find. No idea where I can get a factory one.

    Some questions I have:

    Is there any safety devices that could be causing it to bog down like a sorta limp mode?

    If I crack the thottle more than about 1/5 open, it will bog and eventually stall out.

    I see a T handle screw at the base of the carbs (Low speed?) and another arm with a lever near the top (High Speed?) Base settings for these?

    Any idea what could be causing the bog. I'm not good at reading plugs, but if I had to guess, it's running lean.
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  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Click here for the Polaris service manual.

    The fuel line restrictor must be a specific size in order to create the necessary back pressure for the carbs.

    My guess is that you do not have the correct fuel pressure (wrong restrictor size), and the carbs may not even be set correctly.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Check your compression first.

    Those plugs look like there's n ot enough fuel getting to them.

    Did you clean/inspect the petcock?

  4. #4
    qbzonk's Avatar
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    Quote Originally Posted by xlint89 View Post
    Check your compression first.

    Those plugs look like there's n ot enough fuel getting to them.

    Did you clean/inspect the petcock?
    The entire fuel system has been redone. I did check the petcock and everything was OK. I ran air through it in each selection and checked for good air pressure. My main concern was the cylinder temperatures. They were extremely hot. My old Yami's cylinders never got too hot too touch while idling in the lake.

    The spark plugs looked like it was running hot.

    I may take the carbs off again and check the filters. Maybe they got clogged??

    Fuel returning to tank is a slow trickle. I would love to put the stock one in, but I can't locate one. Manual calls for 0.4mm, but that is pretty damn small. Don't think I could fine a drill bit that small.

    Reeds maybe????

  5. #5
    qbzonk's Avatar
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    Anyone know where I can get thermostat parts for a '94 650SL? I read somewhere these are an issue.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by qbzonk View Post
    Anyone know where I can get thermostat parts for a '94 650SL?
    I read somewhere these are an issue.
    You are in Florida?

    Simply remove the thermostat and the by-pass plunger assembly.

    Check that the cooling lines are not kinked, collapsed, or mis-routed.

    I am not a Fuji engine guy, but I think you can safely operate with the thermostat in warmer waters.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Remove the thermostat. No need to run it, esp. if you're in FLA.

    You can make your own fuel restrictor with a 1/4" barb coupler and a main jet. The PRO 785 uses a #55 jet for theirs. You can do the same, or even a smaller jet if you can find one.

    I did find a bit small enough to make one if the jets don't go small enough. You'll have to do a little calling around to find one though.

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    If you're hell bent on keeping it in, here you go.

    http://cgi.ebay.com/ebaymotors/POLAR...1%7C240%3A1318

  9. #9
    qbzonk's Avatar
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    Quote Originally Posted by xlint89 View Post
    Remove the thermostat. No need to run it, esp. if you're in FLA.

    You can make your own fuel restrictor with a 1/4" barb coupler and a main jet. The PRO 785 uses a #55 jet for theirs. You can do the same, or even a smaller jet if you can find one.

    I did find a bit small enough to make one if the jets don't go small enough. You'll have to do a little calling around to find one though.
    I will check the thermostat and most likely remove it, unless it is OK, which I doubt.

    So are you saying the jet screws into the barb couple and then you slide it into the line? I have the old carb rack, I can probably pull the old jets from it and use them as a fuel restrictor.

  10. #10
    qbzonk's Avatar
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    Any ideas on the hesitating? Am I correct in saying there is only a high and low speed adjuster on this thing. With the LSA near the base and the HSA near the top of the carb opening and it only moves a quarter turn at best.

    I need to know what the best settings would be for these adjusters.

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