cam-end slack

dtkid · Posted: July 25, 2006, 9:34 am Post subject: cam-end slack

Hey Folks:

I'm finally puttin' my 79' XS650 Special back together. However, I ran into a potential problem. When installing my new points (contact-breakers) and setting the timing I noticed something funky goin' on with the points end of the cam. The cam end (not the entire cam) has some slack in it that I cannot remove by tightening the cam-chain tensioner. When I rotate the motor, the cam-end turns fine but if I try to turn the cam-end back against the rotation of the crank, it moves; it moves ever-so-slightly (about a quarter inch) but it still moves. This makes setting the points and timing relatively difficult.

Is this common/normal for these machines? Is some allen-key or something loose and causing this? Should I not worry about it and allow the two cylinders to "share" the error when I adjust the points? Should I take the heads off and inspect and fix it? Thanks for any help you can offer.

grizld1 · Posted: July 25, 2006, 3:08 pm Post subject: Re: cam-end slack

Don't know if this is what you're talking about, but it's normal to be able to rotate the point cam a little CCW by hand and have it return to the original position. The right-hand end of the cam rod is connected to bob weights which throw out under centrifugal force as rpm's pick up, turning the rod and point cam in relation to the engine camshaft, advancing the timing. Springs on the bob weights return timing to the retard position when rpm's drop.

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Yamaha xs650