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  1. #1

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    SL650 running lean

    Hi, I just got a SL650 that everybody and their brother has been working on. The carbs have been replaced with 34mm Mikunis each having their own fuel pump. They were trying to run all 3 pumps off one pulse line which I had doubts about so I took the discs out of the pumps and installed a 3 outlet pump. It also didnt have a restrictor in the return line so I made one as described using a barb fitting and a main jet. I rebuilt the fuel pump and it seems to have good flow.
    All that being said, I'm wondering now if the main jets are too small in the carbs. Does anybody know what size I should use? The carbs all have low speed and high speed needles but even at 4 turns out, its still lean. It boggs even on the water hose. The slow needle adjustment seems to have very little effect also. I have 3 new sparkplugs, 125 psi compression x3 and a hot ignition. I also done a compression leak down test. Everything seems to be ok. Any info on what I need to do now will be vey much appreciated.
    Thanks!


  2. #2
    Canadian Beaver Inspector jkindt's Avatar
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    You could just get the proper carbs and not have to worry about someone else's patch job. I may have a set of 38's available from a 650 if you decide to go that way. I am sure a few others here have extra carbs for sale as well.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Not quite sure why you have smaller carbs installed. Get yourself a set of 38 mm carbs and set them to stock settings.

    Check the fuel pressure.

    How about fuel filters?

    Petcock?

    Gas lines inside the fuel tank?

    Is the autocock installed?

    What size jet did you install in the restrictor?

  4. #4
    I have a set of stock 650 carbs if you need them but they will need to be cleaned and rebuilt.

  5. #5
    lxman88's Avatar
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    i have some 42mm carbs they didnt come off a 650 but they did come off some kina polaris they were giving to me from a loacal shop that someone left behind maybe they came off a 780 not to sure they are bigger then the stocers on my 650

  6. #6

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    The carbs were on there when I got it. No on/off valve, I bypassed it when I found out it was leaking around the shaft. No autocock. Fuel tank is straight, No leaks. I plugged the on fuel line and ran the reserve to the onboard filter/water seperator. It does have a small paper inline filter which it dont need. I will remove it soon. The only jet for the restrictor I had at the time was a 160 (I think) so I used it and right before it is a straw from a WD-40 can. Little bitty hole. Shoots gas almost 3ft at idle. plenty of pressure I would think. I'll try re-jetting. I now have some carbs from a 750 and a 780. The 750s may not be any good but the jets should be ok. I learned today that they were stored half full of water. eewwwwwww! The 750 has 0 compression on one 25 on one and 140 on the third. The 780 was running awesome until it dropped a crank bearing and messed up a fresh piston and cylinder.
    The 650 is just a beater ski to play in the creeks and rivers we have here in the southeast. I have a 99 Ultra 150 when I'm in a hurry.

  7. #7
    lxman88's Avatar
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    i bet if you put the bigger carbs it will run like a raped ape. also your fuel pressure should be like 3 psi at idel and like 6 at ridding conditions if memory seres me right. if you have good compression and good sprak its ither not enoough air or fuel witch the smaller carbs will decress your air no way around that. yes bigger jets will help with more fuel but may richin it to much and just cause it to bog out still

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    A 160 jet is WAY too big to be used as a restrictor. Should be around a 60.

    You need to put a fuel pressure gauge between the carbs and the restrictor to get a reading. 3 feet of fuel spray is no test.

    Yes 1-3 psi at idle and 4-6 psi at WOT is a MUST!!!!!

  9. #9

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    I can manually choke it at the end of the stock flame arrestor (90 degree rubber boot looking deal) and it will run at high speed. I know its lean. @ 92PolarisMike: Do you mind taking one of your carbs apart enough to see what size low speed and high speed jets they have? Thank you much!!!

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by JH1200A1 View Post
    ...what size low speed and high speed jets they have?...
    What year is your SL 650?
    Polaris changed the carb specs from year to year.

    Stock jet size info has been posted previously.

    1992-1993 carb specs

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