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Thread: 1998 Skidoo Summit idling rich

  1. #1

    Default 1998 Skidoo Summit idling rich

    Does anyone have any suggestions with regards to my Summit running too rich at an idle? I go through alot of plugs. Any remedies would be extremely helpful.

    The machine has H.A.C.

    Thanks,

  2. #2
    Member greythorn3's Avatar
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    low compression? needs a rebuild maybe?
    Semper Fi!

  3. #3
    Member mod elan's Avatar
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    Which motor?

    The rotary valve motors were hard on plugs. Too easy to flood when tipped over. Definitely check compression and if possible get an eye on the cylinder walls and pistons for scuffing. If this is all good check the carb settings. My 583 did not like castrol oil. Some 500's were really bad at going thru plugs. I know my problems disappeared after putting a set of NGK platinums in it. I believe they are called iridiums now.

  4. #4

    Default Hadn't thought of that

    I will check compression etc. It does not act, however, like a low compression issue, but I will check.

    It is a 499cc, rotax, (series 1) I am told.

    Thanks for any imput.

    Jdub

  5. #5
    Member AKDoug's Avatar
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    I think, don't quote me on it, that the H.A.C. opperates by applying vaccum to the float bowls to lean out the mixture as the temp or altitude goes up. If it fails, it fails to full rich. My '98 Summit X 670 uses the first generation DPM and it definately fails rich. That could be your issue. You can totally remove the H.A.C. in Alaska, there just isn't enough altitude for it to matter in most cases. You will have to cap off the vacumm lines on the carbs (no big deal) and jet to MXZ500 specs.

    If your only issue is at idle, you can simply lean out the idle mixture by backing out the pilot air screw a 1/4 turn at a time. If a full turn doesn't solve the problem you probably need a different sized pilot jet.

    Does this sled have a primer or "choke"? A "choke" on a Mikuni carb is not really a choke. It's really a starter system that allows fuel to flow freely into the crankcase. When a Mikuni "choke" gets out of adjustment or stuck it will allow fuel to flow too freely and foul plugs at idle.

    How long have you had this sled? Has the problem just cropped up suddenly?
    Bunny Boots and Bearcats: Utility Sled Mayhem

  6. #6

    Default skidoo 500 with primer

    My sled has a primer. I have only had the sled a few days and have already fouled 2 sets of plugs. Other than that it runs like crazy. There must be a simple solution.

    As far as the altitude, as long as I do not take it to the mountains, one setting will work fine, but any hunting or recreating takes place at much higher altitudes. So the altitude compensation is a must for me because I am tired of changing jets on 3 sleds every time I go.

    Thanks for the imput. Keep it coming and I will check out a few of these things this weekend.

    Jdub

  7. #7
    Member AKDoug's Avatar
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    Fouling plugs at idle can also be the result of your oil pump pushing too much oil. How long are you idling it?
    Bunny Boots and Bearcats: Utility Sled Mayhem

  8. #8

    Default skidoo 500 issue

    Ok guys, I did some checking on your suggestions. I think I found the problem, but will not know for sure if I remedied the problem until the weather warms a bit.

    Compression--119 and 120
    Oil pump/cable setting is correct
    Jets are correct.

    Here is what I found when I pulled the main jet plug to check the jet sizes. One carb(clutch side) let the normal amount of fuel drain out, but the magneto side drained out probably about 4 times the amount. So much so that it started draining the fuel from the feed line. So instead of it being a fouling problem, I now believe that it is a flooding problem in one cylinder.

    I checked the float, that did not seem to be stuck, so blew air through the ports in an effort to clean things out.

    We will see. If any one has any additional imput I would appreciate it as I am not a very savvy mechanic.

    Thanks

  9. #9
    Member AKDoug's Avatar
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    Sounds like you might have a stuck needle valve. Look at the float arm. It pushes against a spring loaded needle. That's your needle valve. On a sled as old as yours, it's not uncommon to see them leak.
    Bunny Boots and Bearcats: Utility Sled Mayhem

  10. #10

    Default Stuck needle valve

    Thanks AKDoug,

    A couple of questions in regards to this possible problem. You seem very knowledgeable and I appreciate your imput.

    I had gotten into that last night, but could not figure out how to get to the hex "nut" that holds the needle jet.

    The floats push up against a brass looking double arm, and a tab, in the middle of the connection between the arms, pushes against the needle jet. I could not figure out how to get that set of arms off to get to hex head. I tried just pushing on the pin--I tried using a knife blade on the other side to try to pry it out. Neither try was successful. Any pointers on that?

    By the way, I did "work" the needle and it is moving, seemingly freely. How do I determine if it is not seating properly or leaking or something?

    Thanks again

  11. #11
    Member AKDoug's Avatar
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    The pin that holds the float arms will push out with the proper sized punch. I might take a slight tap with a small hammer, but it should come right out.
    Bunny Boots and Bearcats: Utility Sled Mayhem

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