WORKS ON ALL'01-13 YAMAHA YZ250F and WR250F MODELS - THIS IS A 310cc REBUILD TO YOUR MOTOR, ALONG WITH A FULL RACE PORT AND POLISH TO YOUR HEAD, THAT YOU SEND IN TO US. Used core bottom end - cases, transmission, counter balancer, hardware, etc. All other parts below are new. New BPR 83mm cylinder. 83mm Wiseco forged big bore piston. Nitrite coated piston rings. Hotrods +3mm stroker crankshaft assembly. Cometic 83mm MLS big bore head gasket. Any miscellaneous OEM parts needed. Complete tear down, clean, and inspect all parts. Set piston ring gap. FULL RACE PORT AND POLISH TO YOUR CYLINDER HEAD. 3 angle valve job to your cylinder…