The cr85 and the yz85 have the more powerfull motors , the kx85 is a slug and looks way out of date with the plastics that are on it. Pipe's on the wrong side too. The kx85 is the best for the beginer as its the smallest and has the most linear powercurve. Suspension wise the cr85 is the most agressively set out of the factory but the yz has the best overall action. Depending on what your racing as te cr would be a better SX package due to its stiffer suspension and the yz good for MX. The rm85 insnt a bad ride either and its the halfway point between the kx and the yz/cr. The CR however will become harder to get parts for as production was ceased last year. The yz and the rm though have the single sided shrouds which is a little ugly but you'll get over it.
They are a mini bike still so you have come to the right place. I used to ride a yz80 2001 mod with a 84.8cc conversion and race built motor with shaved and balanced crannk , high comp piston , v force reed block and it used to rip your arms off , Heaps harder to ride than my current 250 and about twice as hard to ride as my 250f. But never the less a scream to ride.
From experience the yz handles like a bmx bike , you could chuck it anywhere and tackle anything. Super easy to wheelie and jump. Whipped good too.
If you where serious about racing though I would check out the Ktm 85 SX or the TM 85. Personally I would get a large wheel as 85's are a preety small bike and you want that height advantage and will get a few seasons out of it.
