rebuild it.
My buddy bought a raptor 660 that didnt even start, not knowing anything about it, we tore it down and rebuild the whole thing, as a learning experience, now that thing starts like it's off the showroom floor, and he spent less than 1/2 of what the going price is for those right now.
Where are you located? If you in michigan I'd be willing to help you out, my garage is the local atv/powersports DIY shop.