If you like working on old Japanese motorcycles with carburetors, you really really want to have a JIS screwdriver. A Phillips will "work" ... but it'll tend to want to cam out of the bolt head, stripping it, especially if the bolts are corroded in place after 40 years. A proper JIS screwdriver has a different bit profile, designed for use with those bolts.

"So just get one, how hard can that be?" I hear you asking. A real, quality JIS screwdriver is expensive, at least in the States. And the cheap ones are often not actually JIS screwdrivers at all. Another option is replacing JIS bolts with allen head bolts, this is very common. But if you are a stickler for keeping things as original as possible ... it's got to be JIS.