The Zipper (1484cc) replaces the Pistons and cylinders, increasing the bore only. The bottom end of the engine is not touched.
There are high (11:1) compression and low (9.7:1) compression kits available. The low compression kit allows the continued use of 87 octane fuel to make about 105 hp, where the high compression requires 92 octane, and a hd starter and slipper clutch in the gearbox are recommended, which will produce about 115 hp.
There is also a 1622cc kit which requires some machine work and change of the cam to achieve 125 hp.