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  1. #1

    2001 GP1200r Piston Destruction

    Hey guys, so I was on the lake this weekend and let someone ride my ski. When they came back to the dock they said it was bogging down, so i took a look at it. Once I started it I could tell something was wrong it was like the engine was knocking and when I would give it full throttle it was not really responsive and would only max out at like 40 mph.I changed the plugs, checked the fuel selector and tried it again but still the same. I ended up checking the compression and cylinder #3 was low and there was no carbon build up on plug from cyl #3. So i took the head off and the piston and cylinder are trashed. It also is missing the power valve. It appears that the power valve just fell off went into the cylinder and trashed the piston. However there are no pieces of the power valve or pieces of the broken off piston. Where could they be, and what caused this to happen? Also i noticed that there is a new oil reside all over the inside of the hull. I checked the oil connections to the carburetor and they seem fine, however carb #3 is oily while #1 and #2 and clean. I am sure I will have to replace the cylinder sleeve, piston, and power valve at the minimum so if anyone has good condition parts pm me plz. But more importantly any thoughts on why this happened or where the oil leak could be coming from??
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  2. #2
    WATER WOODY's Avatar
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    Probably went out the exhaust. Whats in the bottom of the cases? Whats the head look like? Top of piston pics.... Thats why its good to go gas valves or Waveater clips. How bad is the cylinder?

  3. #3
    Rampage's Avatar
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    go check out the classifieds for a piston. I think Jim might still have a used OEM kit left for sale for $30, last time I saw the thread was this afternoon though so his last one could have sold by now.

  4. #4
    Rampage's Avatar
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    nevermind on my last comment, I see that you saw that post already haha

  5. #5
    Here is a picture of the head and also the cylinder. I am more concerned as to what happened?

    WW- there was nothing in the crank shaft it looked pretty clean. so i guess they had to go out through the exhaust.??
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  6. #6

  7. #7

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    The GPR and XLT are notorious for losing cylinder #3 due to the oil line slipping off the brass fitting on the #3 carb. (I have five #3 core cylinders in my garage at this time.) Given what you've described (oil in hull, oil on #3 carb), I'd bet anything that if you pull the stinger pipe out, you'll see a dangling oil line. However, that doesn't explain the missing power valve. Anothe problem with these are the pins on the PV shaft are known to slip out and that will cause the PV to drop into the cylinder/piston. Either way, there's no doubt that you have metal chunks in the crankcase (and bearings...not a good thing).

    So start off by telling your friend that it was nothing they did. It would have happened regardless of the person on it.

    Next pull the stinger and check the #3 carb to see if the oil line coming from the oil pump (in front of motor) is still connected. If not, then you need to do a visual on the crank and look for signs of damage there (discoloration due to heat).

    Let us know what you find.

  8. #8
    Gwsjr.

    When i pulled the stinger off the oil line was still attched to carb #3. It seemed a little lose, and the carb was oily so maybe all of the oil wasnt making it in the cylinder and some was leaking out. I do not have any other ideas about how the oil would have gotten in the hull? Upon looking in the crankcase there are no signs of metal shavings or chunks that fell down in there? I hop this all ended up going out the exhaust somehow. The only hypothesis that i can come up with it that either the power valve fell off and caused this or the piston ring grabbed the exhaust port and caused this.? Either way it sucks. Let me know your thoughts. Also i guess I am going to replace the oil lines for all of the carbs while i have it torn down. Is this the best route or should i go with the block off kit and premix.

  9. #9

    big trouble

    Quote Originally Posted by gnu0316 View Post
    Hey guys, so I was on the lake this weekend and let someone ride my ski. When they came back to the dock they said it was bogging down, so i took a look at it. Once I started it I could tell something was wrong it was like the engine was knocking and when I would give it full throttle it was not really responsive and would only max out at like 40 mph.I changed the plugs, checked the fuel selector and tried it again but still the same. I ended up checking the compression and cylinder #3 was low and there was no carbon build up on plug from cyl #3. So i took the head off and the piston and cylinder are trashed. It also is missing the power valve. It appears that the power valve just fell off went into the cylinder and trashed the piston. However there are no pieces of the power valve or pieces of the broken off piston. Where could they be, and what caused this to happen? Also i noticed that there is a new oil reside all over the inside of the hull. I checked the oil connections to the carburetor and they seem fine, however carb #3 is oily while #1 and #2 and clean. I am sure I will have to replace the cylinder sleeve, piston, and power valve at the minimum so if anyone has good condition parts pm me plz. But more importantly any thoughts on why this happened or where the oil leak could be coming from??
    i had it happen to me and you need to check block for holes.

  10. #10
    I have a 2001 XLT800 with a similar problem. Front cylinder power valve broke just above the pin, letting the power valve fall into the cylinder, where the piston ground off about 1/2 of the curved edge before breaking a chunk of piston off and jamming the top ring into the cylinder wall. On the back cylinder, the power valve broke between the flat portion and the shaft. Cylinder and piston is fine, but have no idea where a piece that large ended up.

    Are you planning to go back with OEM power valves? Or switch to aftermarket and/or install waveater clips? R&D has a billet power valve for about the same price as the Yamaha OEM part. The factory parts appear to be made of powdered aluminum, looking at the places where they broke, so billet aluminum seems like a good alternative.

    Motor had 177 hours on it when it died.

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