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  1. #1
    KensGp kenlepack's Avatar
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    piston and cylinder damage analysis

    recently purchased a gpr1200 off someone who had traded a bike for it and pretty much only rode it once and it sat for a year. At the time of purchase the PO replaced the spark plugs and battery which i thought was nice. it was too cold for a test drive so i took a gamble. When i was finally able to get it out on the water it didnt feel right, not very powerfull at all, something felt kinda wrong, my 98 gp1200 would beat it everywhere. So i researched and find out that he had put the wrong plugs in br8hs, so i replaced with the proper plug and took it out for another ride. it still felt sluggish but after 45 minutes of driving it suddenly lost all power and got loud inside engine bay. i shut it off and pulled the plugs and the front plug was wet and covered in anti seize type compound. brought it back home did a comp test, #1-114, #2-118, #3-115, but do to the look of cyl 1 i took the head off and the cylinder had wet silver compund everywhere. the piston is missing tiny edges around the ports. after lots of reading i beleive the damage was cause by detonation and a lean condition, and or the rod bearing breaking apart and comming up ports. the head is undamaged, these pics are bad but i hope i can get some diagnostic help.
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  2. #2
    KensGp kenlepack's Avatar
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    Well after taking out the engine i found a sweet speed hole in the side of the case. also the cylinder and pistion damage was cause by pieces of the piston skirt and cylinder skirt that went out the exhaust. still not sure what caused it but here are some pics.
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  3. #3
    Happily Self-Employed WFO's Avatar
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    once again crappy pics but you may have lost a rod bearing

    you remove that piston and check the rod and crank?

  4. #4
    KensGp kenlepack's Avatar
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    I will remove the rod and crank after the weekend. If the rod bearing is gone what would be the tell tale sign? because the piston rod does not seem to be flopping around much. and i will most likely just part the ski out now. if the damage wasnt so bad i would have done a rebuild with a spare ski but not sure i might just keep the hull for a special project lol

  5. #5
    KensGp kenlepack's Avatar
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    Ok so i removed the pistons and slipt the cases but nothing seems loose at the bearings. It looks the the piston skirt came in contact with the side of the upper case. i still dont know why, the seals looked good, there was oil in the lower case, everything looked lubed. the only difference i found in that cylinder was that the piston was missing the 2 washers that are supposed to be on each side of the upper rod bearing. could this cause this kind of damage? help pls

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