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  1. #1

    possible rebuild? Questions on diaphragms

    I have an 93 sl650. Last summer the ski would run very sluggish. However, if I pumped the choke and/or turned a certian way, the thing would run great afterwards. I had a feeling it was bad diaphrams, I Just took one off and it looks like it was in pretty poor condition. It had dirt on it and seemed pretty stiff.

    So, I guess my first question is, were my problems being caused by the diaphrams?

    Second, How do i know if I have an oem polaris carb or an aftermarket, and how do I know what diaphrams to buy?

    Third, There seems to be alot of clunking while turning over the engine, which leads me to believe that the crank bearings are bad. There is currently a complete bottom end on ebay, would it be worth picking up?

    Fourth, The ski seems to use rediculous amounts of oil. What would cause this, and should I jsut run pre-mix as an easy fix?


  2. #2
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    Quote Originally Posted by ryanbgb22 View Post
    I have an 93 sl650. Last summer the ski would run very sluggish. However, if I pumped the choke and/or turned a certian way, the thing would run great afterwards. I had a feeling it was bad diaphrams, I Just took one off and it looks like it was in pretty poor condition. It had dirt on it and seemed pretty stiff. Sounds like time for a full Fuel system rebuild.

    So, I guess my first question is, were my problems being caused by the diaphrams?Pumping the choke gave extra fuel,your running in a lean condition,Fix it before you burn it down.

    Second, How do i know if I have an oem polaris carb or an aftermarket, and how do I know what diaphrams to buy?My money would be stock SBN 38 Mukuni's,Get us a pictures of them.

    Third, There seems to be alot of clunking while turning over the engine, which leads me to believe that the crank bearings are bad. There is currently a complete bottom end on ebay Hed to say if it's bad without pulling the jugs,Can you get a video of the sound?I think getting yours rebuilt would be better then buying a used crank unless your buy from some you trust,someone on here might have a good one.

    Fourth, The ski seems to use rediculous amounts of oil. What would cause this, and should I jsut run pre-mix as an easy fix?
    If the cable to the oil pump is broken then the pump goes to max amount or the pump isn't adjusted right,download the service manual from here.With premix you know your running the correct mix at all times.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Ryan, I'm with Keddano.

    Completely rebuild your fuel system inculuding the carbs. The choke and a turn making it better are signs of fuel delivery issues.

    More than likely, you have the Mikuni SBN 38mm carbs. No one would put aftermarket carbs on a 650. But a pic would verify this for sure.

    Engine clunking? Can you verify it's not coming from the jet pump? Maybe the pump bearings are going bad. Audio of the noise would help.

    With the age of the ski and oil pump, I'd go premix to be safe. Besides, you may be removing the engine which will make it tremendously easier.

    You can buy a bottom end of Ebay, but you're unsure of the condition of that one. For $400-$450 you can get a fresh rebuilt crank and know it's good for a long time to come.

  4. #4
    Thanks guys. Anyone know where I can get the diaphrams from? I took the carbs apart today, cleaned them all out, they were in pretty rough shape. Also, the reeds were pretty good shape, but the one was chipped, should I get new reeds too? If so where would be the best place to get both these items?

  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    You can buy individual parts from Randy at Watcon.com, atlanticpowersports.com, babbitsonline.com, or partsland.com.

    Get reeds here. http://cgi.ebay.com/ebaymotors/FMF-T...spagenameZWDVW

  6. #6
    Ok, thanks for the link. I just picked up those reeds.

    SO i'm looking at atleast $100 for the diaphragms? I can't beleive they charge that for those.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Hell, if that's the case, get the entire rebuild kit for around $40 each. Check out Ebay too, I've scored 3 Mikuni SBN rebuild kits for $100 to my door.

  8. #8
    Quote Originally Posted by xlint89 View Post
    Hell, if that's the case, get the entire rebuild kit for around $40 each. Check out Ebay too, I've scored 3 Mikuni SBN rebuild kits for $100 to my door.
    You were right. I got 3 rebuild kits from ebay for $96 shipped. Thanks alot

  9. #9
    Ok, what about replacing fuel lines now? Could I just use clear tubing, or do I need to buy actual fuel line?

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by ryanbgb22 View Post
    Ok, what about replacing fuel lines now?
    Could I just use clear tubing, or do I need to buy actual fuel line?
    The tubing must be gasoline compatible, or the fuel itself can degrade the plastic.

    Buy proper fuel line. It does not need to be high pressure fuel line, as the fuel system operates at rather low pressures, under 10 PSI max.

    You do not want fuel leaking inside your hull = explosion danger.

    And you do not want dissolved plastic inside your carbs and engine = damage.

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