Rocker Box

The Ultima® rocker box is the perfect way to set your engine apart from others. With a unique design and chrome plated aluminum or black finish, this box will enhance the look of any engine. The Ultima® box uses a patented reed assembly to vent all 1992 & later Evolution® engines. Unlike other designs that can degrade in performance with time, our reed assembly is made from fatigue-resistant stainless steel that will give you consistent, trouble-free performance for as long as you ride your bike.

Our compression release box offers classic looks with the versatility to fit on any stock Evolution® or custom engine, plus the added feature of being compatible with the S&S® electric compression release system. All required mounting hardware and gaskets included.

Fits 1992 thru 1999 Evolution® engines.

#89-538 (shown). Compression release compatible Ultima® Chrome die cast rocker box set..

#89-539 Compression release compatible Ultima® BLACK die cast rocker box set.

#77-109 Gasket kit for Ultima®
billet box. (89-514 & 89-516)
#77-111 Gasket kit for Ultima®
billet box. (89-538)

See Below for Exploded View