XS 650 Camshaft Installation TDC Index Timing
You do not have to cut or open the cam chain to install the cam shaft! It will fit on the sprocket under a brand new cam chain with the pairs of ball bearings removed from each end, the bearings will slide right off each end of the cam. To easily install a new chain and peen type masterlink: Click Here!
Degree wheel bolts up flat against charging system rotor. Since the XS rotor is keyed to crank I just turn the motor over from the same side by hand with the rotor.
The camshaft is installed with the flat ground factory index notch (white arrow above) on the camshaft (not on the cam sprocket) facing straight up. The motor is on top dead center on overlap on number 1 cylinder (nearest) in the above image. The two visable cam lobes are both up and the rocker arms, if installed would have both the intake and the exhaust valve open on this cylinder. Number 2 cylinder (rear of image) is on TDC on the compression stroke and both the rocker arms are on the cam base circle with both lobes centered and facing down..
I have discovered that you can check your stock cam timing for all years of the XS motor with the motor completely together and even installed in the bike. This can save many people lots of worry and problems. It can be as simple to check as removing a few screws! When the index notch ground into the camshaft is installed in the proper position as shown in both of my above images: (number 1 red arrow) above, and (the white arrow) in the previous image above it, NOTE the small hole for the ignition advancer at red arrow number 2 above is also facing up, and inline with the cam billet index blank!!!! It sticks out of the cam bearing end seal and is visible by removing the right hand camshaft end cover!! If you have points ignition, you have to loosen the ring nut and simply remove the advance mechanism to see the small pin in the index hole. If you have a 1980 or up with stock electronic ignition you have only to remove the two cover screws and look at the hole!!! It should be straight down (or straight up) (IMAGES BELOW) with the pistons at Top Dead Center (TDC)!! Set the TDC mark on the rotor to the TDC mark on the left end of the crank with a 17mm socket (image below) , have the spark plugs out and see that both pistons are at TDC. It is that simple. This is a BIG problem for many novice engine builders, and now anyone can check the basic cam timing as I have shown here!
Points Ignition cam index pin above is usually facing down, can be 180 degrees out from a prior incorrect assembly and be facing up and still be OK.
1980 Electronic Ignition Cam Still Has Points Index Pin Hole Above
Rotor TDC mark on TDC "T" on RH side of timing tab plate 1980 and Up.
Stock (standard) piston at TDC (top dead center)
Stock pistons and piston rings
Cam Chain Replacement: Click Here!
XS 650 Yamaha Cycle Links, Info & Images: