my dad has a polished and ported 84 yz490, it has a 5 speed out of a 87 yz490, had the head milled to run 110 race fuel he's running 15-46 gearing, and a compleate pro circuit exhaust.
as far as yz490 vs CR and KX 5's if you drop the 5 speed in there there is no comparison between the 3. the yz will dominate |