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  1. #1

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    GPR lost compression

    I was out riding today on my 2000 GP1200R. I ran up to my buddies house, probably 20 miles away. Almost there, I hit a wave and the ski died. Like i pulled the kill switch. Started it back up, it seemed kind of weak for a second, but then seemed to run fine. I took it easy for a few minutes, then picked up the pace a bit. I hit a couple of big waves and it started bogging bad. Limped it to my buddies house, pulled the plugs, 1 and 2 were a little dark and wet but okay, #3 was closed and black. I opened it up a bit, put it together, and test drove it. It seemed okay, but I didn't run it too hard. When I left my friends place a little later, it was a little fussy starting up and at idle, but once I got on it it seemed to run okay. It was definitely down on power, though, and seemed a little rougher. I thought, might be the spark plugs, might be whatever crimped that last one shut. It wouldn't top 50 (on the speedo) and it sounded a little rough, but it got me back to the ramp.

    Got it home, checked the compression. 90-90-0. Maybe my gauge isn't quite right, so the 90's might not be accurate, but the zero is pretty close. I put my thumb on the holes and cranked it, the third one is getting some compression and suction but not as much as the first two.

    I'm guessing on the cylinder numbering BTW, assuming they go front to rear (3 being rear most).

    I cranked the motor and then tried to move the pison down (on the down stroke) with a screwdriver. There didn't seem to be any play. I'm thinking bottom end is intact and piston is at least mostly intact. Obviously I'll know more once I start taking it apart.

    Anyone want to play "guess that failure"? Anything minor that can cause a loss of compression in one of these? I'm not all that familiar with two strokes, never torn one down all the way. I'm sure i can figure it out though, looks like i won't have much choice...


  2. #2
    WATER WOODY's Avatar
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    Sorry to hear this. Pressure test the motor before you take it apart. Take some pics of the heads and piston wash. Time for some parts.

  3. #3

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    What is a pressure test and how do I do it?

  4. #4

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    n/m I did some searching. http://greenhulk.net/forums/showthread.php?t=9408 and http://www.greenhulk.net/forums/showthread.php?t=30838 for anyone reading this thread down the road.

    I don't think i'm patient enough to do that before I take it apart. But I will definitely do it when it goes back together. I want to pull the head off and have a look like now! I'll worry about building special tools and testing everything properaly when i'm rebuilding it. I think once I get it apart it might be obvious what caused the failure.

    Thanks for the advice though, it's the first I've heard of pressure testing!

  5. #5
    Sorry to say but when the gap is "closed" on the plug, that means some metal was flying around in there to hit the electrode. Pull the head, you have problems.

  6. #6

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    yea I kinda knew that. But i'm broke and in denial. I own 5 vehicles, 2 are currently operational. Waverunner, snowmobile, and beater car are all down at the moment. At least boat and truck are operational (although the boat took some abuse this weekend too ). The question right now is, do I turn wrenches, or say "f it" and go boating?

  7. #7
    Hydrotoys's Avatar
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    Go boating. You don't seem to want to generate enough interest to do the troubleshooting or repair correctly. I say enjoy the summer and repair it when you get your head right.

  8. #8

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    Of course I went boating. It was too nice outside not to. But I did get as far as removing the rear section of the exhaust. Hopefully I'll have time this week to tear it down further.

    Believe me, it's not a matter of not having enough interest to fix it right. It's a matter of not having nearly enough time. Or money. Keep in mind that I have never torn down a 2 stroke before. I have rebuilt an engine before, but I have no familiarity with two strokes. That means that I will have to put as much time into learning and research as I will actually working on the thing. Which is a real bitch because I really want to ride it, like now. And I have a 24 hours of lemons race car to prep, a beater to fix, and some repairs to do on my truck and boat so that i'm not down to 0 or 1 running, out of 5 vehicles.

    Just because I say I'm not going to do a pressure test on the motor before I tear it apart doesn't mean I don't have the interest to do it right. Once the thing is apart i'll know right away which chunk of metal broke off and hit the spark plug. My bet is ring or ring land, plus whatever associated damage came from running the thing 20 miles after it broke. Something tells me that the pressure test gauge isn't going to have a "broke ring" or "broke piston" reading on the gauge.

    I've already learned one thing from this thread, that I plan to use at the appropriate time, when I put the motor back together. I will update this thread as I take the motor apart and hopefully back together, and I'm sure I will get some good advice from you guys.

    So far, I kind of got what I expected. I didn't really expect anyone to be able to give me a diagnosis based on what I've got. Hence the "guess that failure" line. Although I did kind of hope that someone would come in with "oh yeah, your kanutsen proportionator broke, happens all the time, $20 fix" or something. Wishful thinking, of course.

    Now all I need is a nice rainy day so that I don't have anything better to do than turn wrenches.

  9. #9
    Is it almost winter yet??? ProXR 440's Avatar
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    I have a feeling you're gonna pull your head and it's gonna look alot like mine... http://greenhulk.net/forums/showthread.php?t=97569

  10. #10

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    Quote Originally Posted by ProXR 440 View Post
    I have a feeling you're gonna pull your head and it's gonna look alot like mine... http://greenhulk.net/forums/showthread.php?t=97569
    Damn! I probably will find about the same thing. Looks like you're local, too, maybe we could console each other over a few beers!

    Looks like you made it to jobbie, though! I was on the south side of the island near the volleyball court in my 27' Fountain. Someone broke my damn windshield, and of course the next day I blew up my ski on the way to visit my buddy in Algonac. Not a good weekend for my toys!

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