Old sportbikes are shit, and so are new ones. :lol:
Their valves work like motocross bike valves. The clearance gets tighter, you drop the shim size until you can't go any thinner, then you have to replace... only a sportbike will cost a hell of a lot more to fix.
Even though they don't wear out in 3-5k miles like an mx bike, they will wear out in 50-75k which is unacceptable to me :lol: