Cam chain wear limit on kz650?

Hello,

I was adjusting my valve clearance and I thought, it would be a good idea to check the wear on the cam chain.
My bike is a KZ650-C3 of 79.
My manuel says "count 20 rivets (the first and the last rivets must be counted) and measure: standard lenght is 160mm, out of tolerance is 162.4mm"
By this, does it actually mean 21 rivets?
Where do I measure? from the center of the 1st rivet to center of the last one? not easy to be accurate!!

If someone knows a different method please help.

Thanks in advance
Fred

20 pins center to center

Measuring center to center 20 pins gives 152mm. What the manual means is, you have to account for pin number 0. Then, the chain is within the tolerance since it is 160mm approximately.

Next time before writing a post with this kind of silly question, I will think twice about it!!

Fred