i wouldn't recommend doing this kind of work without a service manual. you'll also need torque specs as well as other information to get the timing correct, etc. the cam chain tensioner is spring loaded and automatically adjusts when the adjusting bolt is loosened. the adjuster bolt is located at the bottom left of the cylinder. to remove the cam, you'll have to loosen this adjuster bolt and then using a screw driver pushing the cam chain tensioner with a screwdriver, then tighten then tighten the bolt and lock nut. remove the cam sprocket bolt, turn the crankshaft counterclockwise one full turn (360 degrees) and remove the second cam sprocket bolt. remove the cam chain from the sprocket and remove the cam sprocket. use some wire to keep the cam chain from falling into the crankcase. remove the four cam holder nuts and washer and remove the cam holder. remove the cam shaft.
again, you'll need a manual to reinstall it.
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