Mike,

Michelin makes a 150 rear 110 front that works well on the 250. I used them at the end of the season last year and they worked extremely well.

Power 1 150 (B)
Power 1 110 (A)

is what I used. I used them at the last race weekend and 2 long trackdays afterwards. With well over 500 miles on them I would still go racing on them. They are going to last a long long time on the little bike!

Scott