The Hammer 88 big bore kit maintains the engine stroke but converts the engine to a 'square' configuration by increasing the bore
Zipper's has now made a version of its Hammer 88 big bore kit available for use on Harley-Davidson's XR1200 Sportster.
The kit, which maintains the engine stroke but converts the engine to a 'square' configuration by increasing the bore, is offered in two versions; one with emphasis on the lower and middle ranges of power. For big torque figures, the other provides an emphasis on the upper end of the RPM scale creating big horsepower.
Each kit includes Zipper's aluminum big bore cylinders with cast-in ductile iron liners, Zipper's special 3-13⁄16in bore forged pistons, which are claimed to eliminate the need to rebalance the crankshaft, Red Shift cams, Pro-Taper cromoly pushrods and telescoping pushrod covers, and CNC-ported cylinder heads equipped with oversize valves.
The heads feature CNC-machined combustion chambers to match the pistons. Special hardware and a full gasket set are also included.
Finishing the kits off is the inclusion of high flow injectors, an air filter element and a pre-mapped ThunderMax EFI management module for simple plug-and-ride tuning.