BIG TIME RELIABLE BOLT ON POWER! 13.5:1 CP or JE forged piston. Water pump mechanical seal and bearing.No modification of any kind is required to use this kit. Please check your order thoroughly when receiving it. We ALWAYS recommend that this be installed by a qualified mechanic with experience doing this type of work. Piston comes with specific instructions for setting ring gap. If you do not follow those instructions your motor will fail. The item "06 07 08 09 YZ450F YZF450 Big Bore Stroker Motor Rebuild Kit 500cc Hotrods" is in sale since Friday, April 14, 2017. This item is in the category "eBay Motors\Parts & Accessories\Motorcycle Parts\Engines & Engine Parts\Big Bore & Top End Kits". The seller is "bpracingatv" and is located in Upland, California. This item can be shipped worldwide.