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  1. #1

    Wife's GPR chewed a piston. Need advice

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ID:	242863Hey guys, my wifes 2000 GP1200R that was so fast (68.9mph GPS) is not fast anymore. Ski ran great all day Saturday. We went on an extended run, farther than we have ever gone before. We did run both skis wide open some of the way but most of the time was just cruising. We got back and stopped at the local tiki bar. Before we knew it sunset crept up on us and it was too late to ride them home. No biggee since we only live about a mile from the tiki bar. We left the skis tied at the dock overnight. We came back the next morning and the ski was harder to start than normal. Finally got it running but it was making a funny noise. My wife it straight to our house. I got on it and rode it and though the funny noise was gone I knew something wasn't right. Again it was hard to start and once I got it running it would only turn 6000 RPM and 55MPH. I pulled the ski out and did a compression test. The rear and middle cylinders were fine at 120 but the front cylinder was down to 55 psi. I pulled the head this morning and found a chewed up piston. Here are some pictures of the piston. Notice the piece of the piston missing at the exhaust port. Also the piston is chewed up all the way around. Any ideas as to what may have caused this? This is excatly what happened to the middle cylinder last fall that I had repaired over the winter. With the help of you guys I would like to repair this myself if possible. What do you guys think?

  2. #2
    Fortunately the cylinder is still in great shape. I can reuse it but I know at minimum I'm going to need a piston, rings and a cylinder head. Also the PV looks damaged as well so I'm probably going to need one of those as well.

  3. #3
    PolarisNut's Avatar
    Join Date
    Dec 2006
    Lower Michigan
    They're always fast, right before they blow. Piston looks awfully lean. What do the others look like?

  4. #4
    smacota1's Avatar
    Join Date
    Sep 2009
    South of Mason Dixon
    Quote Originally Posted by PolarisNut View Post
    They're always fast, right before they blow. Piston looks awfully lean. What do the others look like?
    +1.....better check carbs and oil lines. Also if the cylinder is off, make sure the crank bearings didn't suffer.

  5. #5
    How can you tell by looking at the piston that it looks lean? I haven't pulled the cylinder off yet. One step at a time. Pulling the head off is as far as I've ever gone into one of the motors so far so I'm not sure what the next step is. I put the head back on to seal out moisture so the cylinders dont rust while I figure out how to go about fixing this thing. Unfortunately I didn't take pics of the other pistons.

  6. #6
    PolarisNut's Avatar
    Join Date
    Dec 2006
    Lower Michigan
    The piston dome is all black...that indicates excessive heat, which is usually caused by a lean condition. Search "piston wash", for more pics and an explanation. Don't worry, the cylinders wont rust, because they are nikasil coated aluminum, not iron. I usually just keep the motor covered with a clean rag, to keep the dust out.

  7. #7
    The other 2 pistons were black as well. Not as black though. I had a felling there may have been a carb issue. The ski would start fine first time everytime. After riding a while then letting it sit for a while it would start fine but when you give it throttle to take of it would cut off. Would do this several times until finally it would run great again. I was hoping to get through the season the do a carb rebuild over the winter. Looks like I should have rebuilt the carbs over last winter. O well, lesson learned, now I need to focus on fixing it. What is the easiest way to remove the cylinder and piston? It looks like I need to remove the entire exhaust. I was hoping to avoid that.

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