nothing is beyond restoration, ive got a couple of dr650s in the shed, both have had cam failures in the past, a common dr ailment caused by insufficient hardening of the cam followers, the hardening wears through and then the cam eats its way through the follower also destroying the cam. this would normally be time for a new one, but you cant get them without spending a lot of cash, so specialists will reapir the cams for a reasonable price. phil joy did both the cams on the bikes i have, he builds up the cam and its follower with stellite, then he machines it back to original specification and hardens it. he also rebuilds cams with altered timing adding lift or duration. so, if you really cant find an xbr cam, but you have one thats not xbr spec but fits the engine, then perhaps you could get it ground and rewelded to original xbr spec. i suppose that the scarcity of spares is dependent on the number of bikes sold originally. so, you should be ok trying to get xbr bits in future, but might struggle with more niche stuff.
