Ummm...what size? Are you talking about dirt bikes or street bikes.
For dirt bikes, the best is KTM in my opinion, but their so freakin expensive its probably not worth it unless you have alot of cash.
Yamaha's and Honda's are cheaper usually for parts and the bike. Kawasaki and Suzuki are pretty close too.
I also depends on what your using it for. If its for trailing, always buy a four stroke. For supercross or track, thats up to you.
