CLASSES

• 500 Premier: 500cc four-stroke OHV and OHC, or 750cc sidevalve machines built before the end of 1968.
• 350 Grand Prix: 350cc four-stroke machines; 350cc air-cooled, single-cylinder, two-strokes with no more than five speeds; 250cc two-stroke water-cooled singles; 250cc twin-cylinder air-cooled two-strokes with no more than six speeds. Machines must have been built before Dec. 31, 1968.
• 250 Grand Prix: 250cc four-stroke machines; 250cc air-cooled, maximum five-speed, single-cylinder two-strokes; 175cc two-stroke water-cooled singles; 175cc air-cooled, twin-cylinder, two-stroke machines with no more than six speeds. Machines must have been built before Dec. 31, 1968.
• 200 Grand Prix: This class combines a variety of engine designs and displacements between 125cc and 250cc, based on an index of performance.
• Formula 750: Works 750cc four-stroke machines, including accurate replicas of Formula 750 machines of the early 1970s. Also includes machines not eligible for Sportsman 750.
• Formula 500: Two-stroke and certain four-stroke machines up to 500cc grouped on an index-of-performance basis, with a Dec. 31, 1972, cutoff.
• Formula 250: Two-stroke air-cooled machines, including singes up to 360cc and twins up to 250cc, with a Dec. 31, 1972, cutoff.
• Formula 125: Certain machines up to 125cc, with a Dec. 31, 1972, cutoff.
• Formula Vintage: Open to machines from 500 Premier, F-750, Formula 500 and Sportsman 750.
• BEARS®: Certain two-cylinder machines built up through 1968 and competing under Formula 750 specifications.
• Class C: Intended for AMA "Class C" machines up to and including those manufactured December 31, 1951, as a ‘51 model. Class C Handshift is a championship class run together with but scored separately from Class C.
• Pre-1940 Grand Prix: 1940 and earlier Grand Prix or modified street machines, including 500cc single-cylinder OHV and OHC and 750cc sidevalve machines.
• Classic Sixties: A class for 1960 and earlier (or like model) Grand Prix/Clubman 500cc four-stroke OHV and OHC machines, or 750cc sidevalve, in basically standard form. Plus 350cc OHV and OHC. Classic Sixties 650 is open to British and European OHC 650cc machines of the period and the Harley-Davidson KH.
• Sportsman: Four-stroke, maximum three-cylinder streetbike-based machines, divided into 350cc, 500cc and 750cc classes. The cutoff is Dec. 31, 1972.
• Novice Historic Production 1972 and earlier production street machines with the standard OEM frame, swingarm, forks and handlebar mounts. Engines use the original OEM bore and stroke. Classes are Lightweight (four-strokes up to 500cc, 250cc two-strokes and certain 350cc two-strokes) and Heavyweight (four-strokes up to 750cc and 350-500cc two-strokes).
• Sidecar: 750cc four-stroke, twin-cylinder, or 500cc two-stroke, air-cooled, twin-cylinder powerplants. Rules available from the AHRMA national office. 
• Vintage Superbike. AHRMA's newest roadrace category includes three classes for motorcycles built up to the 1980 model year and originally manufactured as street machines. Motorcycles are to be as close to "production" appearance as possible. Classes are Heavyweight (unlimited displacement twins and pushrod triples, and displacement-limited fours and sixes), Middleweight (unlimited displacement singles, with limited pushrod twins, OHC twins, pushrod triples and OHC fours) and Lightweight (singles, twins and multis using performance indexes for smaller bikes).

AHRMA 2008 Michigan Engineering
Historic Cup Roadrace Series