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  1. #1

    Cam issue .....Need help

    1.8 NA Yamaha motor

    We have an issue where cam turns freely until it is bolted down, then it binds and we have already cracked one. Timing chain broke, we replaced tensioner and all valves, keeper and springs. Head seems to be ok, as well as the brackets that hold down the cam. Valves move freely with out the cam bolted down. Anyone have any ideas?


  2. #2
    rcab85's Avatar
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    Yup, same reason why your timing chain broke the line bore is off or your cam caps aren't on properly.

  3. #3
    if you're doing it by the service manual you may be reading it wrong and bolting down the caps too tight as the specs are in/lbs not ft/lbs. You'll need a different torque wrench for those specs as they are no where near as tight as if it was ft/lbs and you'll lock up the cams.

  4. #4
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Interference motor if you are cracking a cam when you are tightening it down. Reason is you have a piston on top dead center and you are installing cam with lobe pushing down on that cylinder, and it pushes the valve into piston locks it up and snaps cam.
    The way it should be done is put number 1 on top dead center then install exhaust cam as close as you can lining up the timing marks (and then torgue it down to 11.8 ft-lb or 141.6 in-lb) Then install intake cam and line up the marks and torque them.

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  6. #5
    Guidoo's Avatar
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    Are you 100% sure the caps are in the exact location as it left the factory?

  7. #6
    gp1200rider's Avatar
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    You can bolt down 1 cam on the bench and spin it, and check valve clearance and bearing clearance.

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