Stock motor is the 650cc, but it has a new top end kit installed. The work was done at the outdoor toy store in Carson WA. My friend Rick Estey owned the store. And the guy I got the rhino from put about $20K into upgrades, including a lift and tracks. So the motor was built for more torque with a larger carb, and bigger cooling system. But the track system was a failure, kept breaking. So it was removed and lift kit was removed. We drove it around for about an hour yesterday, the starter was i bit draggy, then after parking it, the starter doesnt turn the motor and there was an electrical smell along with a little smoke.