Hi there David.
Is it thickness before being crashed including the convex to want to know you?
Regretfully I do not know me either. I cannot measure it precisely when I do not buy a new part.
This is because it does not buy it as far as it does not open an engine.
The thickness does not appear in a service manual either.
(As a matter of course, because it is a premise to use the new parts)
I thought that I was out of stock for my memory at one time, Because I have a worn gasket.
There is the stock now if I examine it. But, it is very higher.
Because part charges for Safekeeping are added, it is very high.
Specifically, the part search is possible from the HP of Yamaha.
historic bike/同意する=consensus(right bottom)/検索=Search
You can examine of parts list.
But we have not service manual of PDF.
Because it is a maintenance book of the motorcycle more than 25 years ago.
We have only a Japanese service manual.
I think that there is an English service manual in the field if exported.