I have a 2011 KFX 50 atv that I installed a new Wiseco 80cc piston kit on and it runs great. I installed a new battery and starter, brakes and tires are great, this ATV looks amazing. I would let it go to an Aldeer member for 900. A KFX is a 4 stroke atv and the only difference between the 90cc and 50cc is the tire size and piston size this is a versatile atv for kids.