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Thread: A little technical help...

  1. #1

    Default A little technical help...

    Hey guys, have a tech question for those who may want to tackle it.. because it is starting to get to me, and was wondering if you may have any suggestions.

    I have an arctic cat 99 ZR500 that I recently aquired that has been sitting for a few years, and have had to do a LOT of work on it, and I still can't get it to run right. Right now I have a great idle, and great running up to about 6,000 RPM, but just can't get it well over that.

    Carbs - have already cleaned the living crap out of them, fiddled with pilot and idle screws, moved the jet needle up and down, and changed for a few different main jets, the stock, which is a 340 is what is in there right now, and I have it at the carb setup it seems to like most so far.

    I tested the compression, and both cylinders are solid at 120psi. Both spark plugs gapped and brand new, and terminals cleaned with electrical cleaner. I disconnected the TSS system to make sure that wasn't it.

    The fuel system has been completely emptied bone dry to get whatever reminents of water and crud out of it, tank cleaned, new fuel filter, and syphoned new gas through the system to make sure everything was out of it. Same with the oil.

    So what is next... I have checked the spark plugs, and by the color, a light brown/tan, they seem to be running right about where they need to be on the lean/rich way. If I use less throttle, I can get a few more rpm, which is why I am thinking of putting in some giant gets like some 370's to test... but I'm tired of taking the carbs apart. And when it gets over 6,000, it's not bogging, it is just plain missing.

    So my next ideas are,
    -Getting ahold of a multimeter and checking my ignition power levels.
    -Checking with bigger jets (even though I've been up and down a few times)
    -Finding someway to test the fuel flow to the carbs, see if it is a slow pump - any ideas on that one I would appreciate.

    It runs awesome up to about 6,000, then cuts a little bit, once it gets up to 6,500 it is done, and starts missing quite a bit, won't give me any more. Anything else anybody can think of that I have forgotten?

  2. #2
    Member SusitnaAk's Avatar
    Join Date
    Feb 2007


    I would go after the pump, Missing like that could be sign of not enough fuel, Or timing.. If they sit like that the diphrams in the pump might have gone bad. When it start to do that flip choke real fast on/off see if it picks up speed.if that works thinking fuel. If not then spark, Check the wires to cdi box make sure they are not rubbed, I have had two machines act like that a John Deere, and Polaris.Went to change the CDI box out and found the wire was rubbing grounding out, IT too was at high RPMs The Engine Was leaning on the wires. Hope this helps , Do one at a time. Sometime these thing drive you nuts. Let us Know what you Find

  3. #3
    Join Date
    Jun 2006


    Are you running it with the belt on or off. Don't forget to check the clutch. Clutches do funny things to engine power if they aren't functioning properly.

  4. #4


    Yeah, the guy at the cat shop here in Wasilla said the same thing... good chance of it being the clutch... Gotta get it pulled.. I know I'm not wasting my time, because even if it isn't that, I'm sure that it needs to be cleaned and oiled anyway.

  5. #5
    Moderator AKmud's Avatar
    Join Date
    Oct 2005
    Wasilla, Alaska, United States


    You may have a weak CDI box. Don't rule out an electrical/ignition problem just because it runs well at low RPMs.

    My $.02

    The porcupine is a peacful animal yet God still thought it necessary to give him quills....

  6. #6
    Member Erik in AK's Avatar
    Join Date
    Jul 2006


    Is the compression good?


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