JT Engine Works has a great reputation for custom Kawasaki KX500 engines.
Some of the customizations include:
Many machined billet parts. Fat head with decompressor built in, custom ignition cover, changeable domes, KX500 tech shift kit, Boyesen water pump cover, TSR billet clutch cover, TSR power valve linkage and TSR cases with machine engraving, ignition cover, v-force 3 reeds, JT Engine Works center power valve cover and Cerakote.