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  1. #1

    Lightbulb Yamaha GPR1200R motor started getting noisy and shaky, then i shut it off!

    Yamaha GPR1200R motor started getting noisy and shaky after cruising at 30 mph, then i shut it off! Almost sounds like a lifter tapping in a car? Motor is shaky and it lost a lot of power.

    - Motor is free spinning and turns over with ease.
    - Pulled plugs and visually inspected into cylinders, no trash or debris.
    - Plug were all oily (and probably need replacing)
    - Spun motor over without plugs and sounds ok.
    - Checked compression ....and here is where i think i made a discovery.

    Cold compression #1 - 104psi #2 - 90psi #3- 106psi. The difference in pressure was kind of alarming to me because this motor had a top end rebuild 60 hrs ago. After a closer inspection into the cylinder of #2 i noticed it was almost dry looking in there compared to the front and back cylinders. So i poured several drops of amsoil 2 stroke oil in the cylinder and bumped the starter a few times, then rechecked compression and it was up to 100-101psi. ???

    I am not using the oil pump system and i am running premix @ about 30:1

    I'm scared the problem may be elsewhere but after seeing this i am going to make an educated guess and say needle stuck closed on #2 carb and ran dry briefly? The noise i was hearing was possibly the #2 cylinder not being fired and it being pulled around by the other 2 cylinders?

    I'm fairly mechanically inclined and i am at the point of pulling the motor to have a better visual inspection, pull and clean the carbs, and power valves. I have the exhaust almost out. But im stuck at this infamous last bolt on the manifold the closest to inside wall on port side...uurrrggghhhh

    Am i on the right track here or do i need to pull motor and tear it down completely, which i may or may not be able to accomplish. I did have a service manual printed out for assistance....

    Any thing else to look into, that anybody can think of? Its very frustrating because i bought it from a friend to ride my daughter around on very recently and i have only put 2 hrs on it.

    Thanks in advance!!!


  2. #2
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    Pull the spark plugs and look down the hole

  3. #3
    Almost's Avatar
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    It almost sounds like you spun a piston ring. That happened to me but with 167hrs on the top end, but it could be many other things as well. I would pull the head first before pulling the whole motor and go from there.

    if your spark plug gap hasn't been smashed closed by loose metal the damage could be minor since you shut if off quick.

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  5. #4
    Quote Originally Posted by riick370 View Post
    Pull the spark plugs and look down the hole
    as stated i visually inspected inside cylinder when i pulled plugs out.

  6. #5
    Quote Originally Posted by Almost View Post
    It almost sounds like you spun a piston ring. That happened to me but with 167hrs on the top end, but it could be many other things as well. I would pull the head first before pulling the whole motor and go from there.

    if your spark plug gap hasn't been smashed closed by loose metal the damage could be minor since you shut if off quick.
    I inspected every way i could without pulling head and saw no debri in cylinder. Only noticeable thing WAS the middle cylinder seemed dry..

  7. #6
    Almost's Avatar
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    You might not see anything, I didn't see anything either. The only evidence something was seriously wrong is when I noticed the plug was crushed shut.

  8. #7
    Quote Originally Posted by Almost View Post
    You might not see anything, I didn't see anything either. The only evidence something was seriously wrong is when I noticed the plug was crushed shut.
    Ok, ill check again. I did closely inspect the spark plugs and they looked great as well. Seems the noise only appears when it is running? If i pull the head i cant reuse the same head gasket can i?

    Thanks for the help so far.

  9. #8
    Pull the head

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  11. #9
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    Quote Originally Posted by geront View Post
    If i pull the head i cant reuse the same head gasket can i?
    Some say you can and some say no. I can tell you I wouldn't use it again and service manual says the same. Some people use copper spray and use it again but it's not recommended.

  12. #10
    OK. So ive been very busy this afternoon. Went ahead and pulled the head off. No problems found visually. Then as i was turning the engine over by hand i was feeling the pistons as they moved, looking for play and #2 piston as soon as i start the downward stroke i can push on the piston and i feel it give a little...i can easily see why i would have a loud chattering noise now. I'm thinking i was correct from the start and now the wrist pin bearing has failed. Ive already removed the engine and have it ready to tear down more. Tomorrow i will remove the jugs and inspect further.

    If the wrist pin bearing IS the problem...wear do i go from there. Am i going to need to tear the block apart to clean it out?
    Am i going to need a new rod?

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