At Chapman Performance, we are experts at obtaining the most horsepower and torque out of 4-stroke engines.  With hours of testing comes knowledge and reliability.  We are relentless in our efforts to find extra horsepower. We build and maintain all major brands of motocross bikes.  Whatever your need; from maintenance to a complete bike build, we have a solution for you. Cylinder porting Precision head modifications Install guides Custom valve building Recrome cylinder Big bore kits Crank rebuilding Custom transmission building Carb modifications Radiator modifications Coated radiators If you are looking for unsurpassed service, contact us today.