The 2 cylinder Rotax cylinder reed valve designed motor with the reed valves mounted onto the cylinders offers more power than the 583 rotary valve motor. Twin trail pipes will net 10 HP with 3-4 pounds of torque @ 8200-8300 RPMs. V-Force 3 Reeds will enhance this motor without a doubt. We highly recommend trail porting with Crank Shop pipes. Trail porting has a 6-8 HP gain with 4-5 pounds of torque. For race modifications the Improve Stock Package turns @ 9200 RPM's with 140 HP - 81 lbs. torque and the Prostock Package is 157 HP @ 9400 RPM's 88 lbs. of torque. Both motor packages will run a race fuel such as C12 or C14. Race packages are not for a trail motor. The labor to disassemble, clean, and assemble the motor is NOT included in the package price. Any crank work, repairs, or replacement OEM parts would be an extra charge.