How many depends on which engine is being discussed. They originally used them on ALL the studs. The point of those things is to gasket oil from coming up the oil journals so they are really only needed on the outside four studs. On 903cc engines and early 1015cc, they used them on all the studs as I noted but switched to steel washers on later 1015cc engines. If you want them to seal good, heat them with a MAPP or butane torch till they are red hot and drop them into cold water. This process is called annealing and restores their ability to seal. Last note... I have purchased K&L cylinder stud nuts. They are replacement for the acorn nuts that came on the bike originally. The K&L nuts are not quite large enough diameter and you WILL get oil leaks around the oil journals on the outside four studs if you use them. Use the original Acorn or APE sells a nice replace set that is wider and does a good job sealing. The chromed acorn nuts often get ratty looking and rusty over time and if you paint them, the paint is scarred up when they are torqued.
wiredgeorge Motorcycle Carburetors
Mico TX
www.wgcarbs.com
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