With the timing marks at TDC, jam a wood skewer in the hole in the end of the crankshaft to hold a string in the hole. Pull the string up to sight on the notch in the camshaft boss, making sure that the notch is parallel to the line.
Perhaps is helping but I still found it Difficult -- Jokingly
One hand holding the string
One hand holding the left end of the cam chain
One hand holding the right end of the cam chain
Head over at the backside of the Cam sprocket to watch the marking on the sprocket
One hand for the Chain link at the same time pulling the right and left together.
In my case the rotor timing mark was gone because of a rewinding ..marking not at the right spot
So I had a wood stick into the spark plug hole to find TDC
So when the both ends are in place cam and crank OK .
Which can take a while one tooth wrong on the cam is not mowing the marks that much
and then all wires Needed as safety are gone that can be there for picking it up
preventing it to fall all the way down hanging out on the underside.
With at least -- at least a half hour to fish it up again.
The cam is in right position .you have one hand for pressing the ends down on the sprocket
And with tho other one hand the link pins shall come into the cam chain end .
With a " Thick " Head gasket it might not go easy
If the thumb pressing ends down is not there for a moment
Trrrrr..rrttttt and the chain is down the hole. Gone
I am not a very good mechanic and some days you are on a flow / roll everything goes fine and things get in place effortless
Other days not so .. I suppose all have done that .. After straightening out the back Cleaning hands with a rag
finding another piece of metal on the workbench.
A small washer ..or a spring or even larger parts I forgot to put in the axle for Starter motor.
Last time --- but was lucky in the sense that I have taken away the starter motor and has kick only.
Of course simple jobs can be done the wrong way..
This is a job most people seldom do so if a friend is available.( assuming XS 650 owners have friends / Joking again )
It might save time and money not needing the chain rivet tool.
I have not read the Instructions by Jim mentioned here .Put this here anyways can be a help in the sense that the preparations can include having a friend with strong hands good eyes and a couple of beers ..Close By.