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  1. #1

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    Sunk GP1200R, lost compression

    So, here's the story. Over the winter, I removed the catalytic converter in pieces, and installed a D-Plate... Went out to the lake for the first time of the summer, fired it up and rode it across the lake... it ran like a champ! Parked it for a few hours to set up camp... when I got back to it, it was cranking slow so I thought my battery was dead... went and bought a new one... when I pulled the seat off, there was water in the hull... (one of the plugs wasnt all the way tight) and it had sucked water while I was trying to start it. so I put it on the trailer, drained the water, pulled the spark plugs, and purged out the water... installed new plugs and got it started.... idled a little rough, but cleared up after a minute.... ran it across the lake and it ran great. A buddy of mine got on it, and took it for a ride and it died on him... now I have no compression on the #2 cylinder.... I'm thinking I'm going to pull the head off first, and if nothing looks damaged, look into the reeds.... anything else you guys can suggest? anything special I should know?

    Any help is greatly appreciated!


  2. #2

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    If you have no compression on that cylinder.....then when you pull the head you will find damage for sure.

  3. #3

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    Thats what I'm thinking... can a broken reed cause lost compression too? looking through the spark plug hole with a flashlight, the cylinder wall looks good... worked on lots of 4 stroke stuff, but never a 2 stroke.

  4. #4
    Happily Self-Employed WFO's Avatar
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    Quote Originally Posted by DCB_MINDED View Post
    Thats what I'm thinking... can a broken reed cause lost compression too? looking through the spark plug hole with a flashlight, the cylinder wall looks good... worked on lots of 4 stroke stuff, but never a 2 stroke.
    if you have no compression, there is a problem with the piston

    pull the head and see

  5. #5

    Join Date
    May 2011
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    I had the same problem and it had a slight hole burnt on the side of the piston and i could actually see the rings causing no compression.
    I will also take the head off first as the problem will be there as compression from the piston top to the plug is a problem.

  6. #6

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    Plan on yanking it apart tonight... hopefully not too much damage... It sucks to spend a fortune at the first of the year to get it running again.

  7. #7

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    Feb 2011
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    South Carolina
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    apparently the dreaded oil line failure strikes again... somehow 2 of the lines managed to pop off... looks like the cylinders took only minor damage and will clear if I have them bored... gotta buy new pistons though... recommendations? Anything that I should check or replace while I have it apart? Pics are on the way...
    Thanks for all the help guys!

  8. #8
    Mr. Millennium's Avatar
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    Jul 2010
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    You need to use riva yamaha oem parts they work much better.Also take the oiler off go to premix wont have this problem. Riva sells a block off plate for the oiler and is very simple to install.

  9. #9

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    Feb 2011
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    Just spoke with my local Yamaha shop... They told me you cant bore the jugs on powervalve engines. Is this true? Doesn't make sense to me. If I have to buy new jugs, I'm not sure I'm willing to drop that kind of money into it.

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