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  1. #1
    Join Date
    Dec 2009
    So Central Mn

    Default 1998 MXZ main jet sizes

    Hi all,
    hoping someone with some experience with these 670s can help.
    I picked this thing up last spring.
    Its in pretty good shape.
    It has about 4100 miles on it.
    This is my "brother in law sled," so it doesn't have to be perfect.
    I just don't want to dust the engine due to improper settings.

    I know the engine has had work done, since the green base gaskets stick out.
    (Betting Rotax wouldn't let it leave the factory like this.)
    I don't know what was done; guessing top end.
    It pulls over hard; like all 670s do.
    Has 130 PSI each cylinder.
    Stock jets are PTO 310 MAG 290, which is correct from the small research I have done.
    Plugs are the BR9ES, which I think are correct as well.

    It has a single PSI stinger pipe with a can on it.
    DO I need to change the jets out or plugs?
    I found that PSI is no longer in business when I was looking for info.
    It seems strange to me jetting/plugs weren't changed when the exhaust was modded.
    I didn't really run hard when I bought it because there wasn't much snow, but seemed to run fine.

    It looks like it has an EPI Performance Trail Clutch kit in it too.
    Springs are newer, blue and red, same ones that Dennis Kirk sells.
    I know this may not affect the carbs, but all of this together..............

    I don't have any of the stock parts, so that isn't an option.
    This is the first older Ski doo I have had.
    With other sleds I usually didn't mess with
    stuff for fear of burning up the engine.
    This one was a deal.

    If anyone has any advice,
    Thanks in advance!

  2. #2
    Join Date
    Jan 2010
    Green Bay, WI / Lakewood, WI


    You might want to check this out over on Dootalk. Tons of folks over there know these pipe/can combos inside and out. If you still can't find the info you need you need to just go by seat of your bibs and check the color of the plugs.

  3. #3
    Join Date
    Dec 2009
    So Central Mn


    Thanks gpt, I will do that.

  4. #4
    Join Date
    Dec 2009
    Merrill,Wi - Mass City,Mi weekends


    Look for a Stock exhaust. That Pipe is not welcome on the Trail and you will pay a Fine for it.

  5. #5
    Join Date
    Jan 2010
    Live in St. Germain/ work McHenry il


    Quote Originally Posted by longtrack View Post
    Look for a Stock exhaust. That Pipe is not welcome on the Trail and you will pay a Fine for it.
    I agree with this comment if you are going to trail ride the sled in WI. or MI. they both have exhaust noise laws and the aftermarket exhaust build back then are not going to meet the allowable db. The 670 ran good from factory. Should be plenty of used stock exhaust for this sled. If you want to stick with that exhaust most aftermarket exhaust require you to go up one jet size over stock.

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