SPI vs Wiseco Pistons

Many people ask what the difference is between the SPI & Wiseco pistons for the Kawasaki engines. One of the things I tell them is the Wiseco finish looks much better, as you can see in these side-by-side photos.

The SPI uses an L style top ring similar to the original pistons in the Kawasaki Invader/Intruder, while the Wiseco uses a standard 2-ring design like the versions originally in the John Deere Liquifire/Sportfire, which had been changed from Kawasaki's original design per JD's specs. However both pistons are interchangeable in both engines.

The Wiseco's are forged (molded & cut from solid material), as opposed to the SPIs which are cast (poured into a mold). The forging process makes for a much stronger end product.

One big plus for the Wiseco is that they are made entirely in the USA, while SPI is made in Taiwan.

SPI 440cc Kawasaki/John Deere Pistons  

Wiseco 440 Kawasaki/John Deere Pistons