Rocker Arms & Parts
About Rocker Arms & Parts
Rocker arms pivot on shafts and turn the pushrod's movement into valve opening. Riders replace them or their shafts and studs when the pivot surfaces wear, when the engine develops noise or oil leaks at the rocker box, or when they want roller rockers or a different ratio.
The arms are not identical from position to position, and listings name the position, such as front exhaust or rear intake, so check which one you need. Roller rocker arms are listed with a ratio, such as 1.5:1, and a higher ratio increases valve lift, so check spring and clearance before you fit them. Shafts, stud kits, shims and washers are listed as separate items. Rocker boxes, the housings that cover the arms, appear here as well, in die cast and chrome versions. Match the engine family and year, such as Shovelhead, Twin Cam, XL or M8.
Brands here include Colony, Jims, Ciro, Drag Specialties and S&S Cycle. Rocker arms work together with Push Rods, Engine Valves and Camshafts. The whole group is Valvetrain Components.
FAQs on rocker arms
What does rocker arm ratio mean?
The ratio is how far the valve moves compared with the cam lobe's movement through the pushrod. A 1.5:1 rocker gives about one and a half times that movement, so it needs matching springs and clearance checks.
Are rocker arms sold as sets or individually?
Both. Some listings are for one arm in a given position, and others are for sets. Read the position and quantity in the listing, since front, rear, intake and exhaust arms can differ and the wrong one will not work.
Why are rocker arm shafts listed separately?
The arm pivots on the shaft, and both wear. If a shaft is worn, the arm and shaft are normally replaced together, so the pivot clearance is brought back within the limit in the service manual instead of staying loose.
What are rocker arm shims for?
Shims set the side clearance of the arm on its shaft on some Harley-Davidson engines. They come in thicknesses such as .007 inch, and the service manual gives the clearance to aim for, so measure before you choose a shim.
