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Thread: Mountain Cat Problem

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    Member sayak's Avatar
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    Default Mountain Cat Problem

    I have an AC Mountain Cat 570 fan, 2 carb. An '03 I think. It ran great until last spring when we were out camping and I started it in the morning and it ran like crap. In pulling the plugs I found that the left side plug had some metal in the gap. I cleaned it, and it ran, but wouldn't idle. I was able to get it home by not backing off the throttle and amazingly it runs OK at speed. Has plenty of compression in both jugs. I started it last weekend and it will run as long as I don't let off the throttle.

    My theory is that some little piece of carb got pulled into the cylinder from the left hand carb, though I haven't pulled it to check yet. A jet of some kind? Any ideas or input would be appreciated. Thanks.

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    Moderator LuJon's Avatar
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    Metal in the jug is never a good thing! Personally I would pull the carbs and top end. A carb rebuild kit and top end gaskets would be worth the peace of mind. I would pay particular attention to the reeds as that is the most likely source (IMHO) of metal since they are the biggest highest stress mechanical object in the intake path.

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    Member Dupont Spinner's Avatar
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    Quote Originally Posted by sayak View Post
    I have an AC Mountain Cat 570 fan, 2 carb. An '03 I think. It ran great until last spring when we were out camping and I started it in the morning and it ran like crap. In pulling the plugs I found that the left side plug had some metal in the gap. I cleaned it, and it ran, but wouldn't idle. I was able to get it home by not backing off the throttle and amazingly it runs OK at speed. Has plenty of compression in both jugs. I started it last weekend and it will run as long as I don't let off the throttle.

    My theory is that some little piece of carb got pulled into the cylinder from the left hand carb, though I haven't pulled it to check yet. A jet of some kind? Any ideas or input would be appreciated. Thanks.
    Check the reeds!!!!!!! As far as a carb rebuild there is little to rebuild unless changing jets/needles. A good take apart and flush is always helpful once in a while. Also take a good look at the carb booths for cracks. If you find nothing on the tear down there, go and pull the head ( I hope not) but it may have peeled some nikasil off the wall.

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    Member mainer_in_ak's Avatar
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    As much as I hate to tear down a motor, it's time to pull it apart if you've found metal in your cylinder. You're lucky to have gotten a "sign", and consider it a blessing. If you continue to run the motor, you may cause more damage that it's worth. Simply pulling the top end apart and checking the reeds may not be the best idea. Crap can get down near the crank in the lower end. You could essentially do all this work to the top end, only to discover that their is some bad stuff hanging out around the crank. It's stressful to have to pull the motor, but pull the motor out, and take it completely apart. The fan cooled suzuki motor will be a simple motor to work on. If you're going to do the work, do it right. Hard telling what's hanging around the crank shaft.

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    Member AKDoug's Avatar
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    The first test is an honest to god pressure check. Get a compression tester and check each cylinder. You should be right at 125lbs and the two cylinder should be close to equal. Check the reeds and cases, if you are missing any part of the reed petal it most likely went through the engine. If it's missing part of the cage you may need to go look for the parts. You don't need to pull the motor to check it. Pull the fan shrouds off, remove the head (one piece for both cylinders on this engine) and take a look. If the cylinder walls are smooth and the pistons look good, you are probably O.K. It's only a few more nuts to pull the cylinders off and look down inside the crankcase area.

    I once detonated (bad fuel) most of the top of a piston off a Summit X and seized it tight. We were able to get it running again and rode it out. You would be surprised at how much damage a top end can take and still run, but not run quite right.

    I wish I were closer, I'd be more than glad to help out.

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    Member sayak's Avatar
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    Thanks, all you gentlemen.
    I expected the worst when I saw that little speck of metal between the electrodes. Unfortunately, I have no shop or garage, and my hands are not what they used to be for making "trail" repairs outside. I'll probably wait until the budget allows and take this machine to one of the shops hereabouts. Again, thanks.
    Steve

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    Are you shure it was a pice of metal i had the same thing happen from carbon. When i pulled the plug i thought it was metal but it was carbon..
    I have a 2004 570 m1 mountin cat. I had it start running like **&^ i cleaned the jets and flushed the carb and it was fine.
    Just something i would check..

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    Member sayak's Avatar
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    Quote Originally Posted by matsuthunder View Post
    Are you shure it was a pice of metal i had the same thing happen from carbon. When i pulled the plug i thought it was metal but it was carbon..
    I have a 2004 570 m1 mountin cat. I had it start running like **&^ i cleaned the jets and flushed the carb and it was fine.
    Just something i would check..
    Pretty sure. It was a shiny little ball.

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    Member AKDoug's Avatar
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    If I end up heading that way this winter I will let you know and bring the tool box

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    Quote Originally Posted by sayak View Post
    Pretty sure. It was a shiny little ball.
    With good compression I am believing less and less a cylinder problem. A shiney metal piece sounds like a piece of the stock reed came off.

    I would be happy to give it a looksey. If Anchorage way bring it with you. I am betting we will find it quickly. Significant other shopping you and me ripping in a heated shop.

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    Member sayak's Avatar
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    Thanks for the kind offers guys. I have a guy lined up to look at it next week. Hopefully he'll get to the matter quickly.

    The reason I thought it might have been a portion of the intake system getting ingested by the cylinder is because I had it happen once on a Volkswagen many years ago. It continued to run, but poorly. A mechanic tracked down the problem for me and told me it was a small brass orifice in the carb which had come loose and got pulled into the jug. Surprisingly it seemed to have done little damage to piston, cylinder or valves, and after the carb was repaired, ran well again. A piece of reed sounds plausible and I hope that is what it turns out to be.

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    Dupont you selling bulk 2 stroke this yr?

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    Member Dupont Spinner's Avatar
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    Quote Originally Posted by 323 View Post
    Dupont you selling bulk 2 stroke this yr?
    Yes I am, already working my second barrel for the season.

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