Dirt Track Tech Inspection, Modifications

d) Arider must make every effort to use the same motorcycle in a heat race as he/ she does in the main event (if transferred). If a replacement bike is necessary, the rider must start the main from the penalty line.

14.4 DIRT TRACK TECHNICAL INSPECTION & MODIFICATIONS

a) TIRES: Knobby tires are not permitted. The use of 19-inch wheels and new tires is encouraged, for the safest and most predictable setup. The maximum tire size (both front and rear) for vintage classes, up through Sportsman 750, is 27.0x7.0x19. Seventies Two-Stroke/Singles and Four-Stroke Super Singles classes may use “wide” 27.5x7.5x19 rear tires. If you have questions, please contact the Dirt Track Rules & Eligibility Committee. b) WHEELS: Rim width must not exceed WM3 (2.15”) for all vintage-era classes, from Dinosaur through Sportsman 750. c) BRAKES: Brakes are not permitted in Dinosaur or Classic classes. As an alternative to brake removal, an effective mechanical lockout may be used to disable rear brakes for these classes. Any disc-brake caliper with up to two op-posed pistons is acceptable for Sportsman. Operating front brakes are not permitted in flat track racing. Hydraulically-operated drum brakes are prohibited. d) CHASSIS: Must be of the same period as the class in which the machine is entered. Dinosaur machines’ chassis and engine must be made by the same manufacturer (i.e., OEM chassis or replacement type offered by the engine manufacturer). Frame modifications for Dinosaur class must be of period style.

Weld-on rear axle holders are permitted but bolt-on adjustable-height rear axle supports (i.e., Sonicweld type) are not. e) Swingarm frames are allowed in Classic classes only if they are production components for that make and year motorcycle and equipped with stockconfiguration swingarms.Any aftermarket racing frame must be of rigid type (hardtail or strutted) to compete in Classic classes. Post-1967 Champion, Redline,

Trackmaster, Ossa DMR, Bultaco Astro and similar-type dirt track frames are not allowed in Classic classes, even if fitted with struts.Aftermarket frames cannot be used in the Classic Open TT class. f) Sportsman-class machines may use a production chassis from 1974 or earlier, or an aftermarket chassis of the type and configuration used in NorthAmerican dirt track competition prior to 1975. Typical eligible models include Champion,

Trackmaster and Redline. Others must be submitted to the Dirt Track Rules &

Eligibility Committee for an eligibility decision. Requests must be accompanied by documentation and photographs establishing the configuration and appropriate timeline. Accurate replicas of eligible dirt track aftermarket chassis are acceptable as long as they conform to the original design and other class rules.

See roadrace rule 9.7.3f for a diagram of a braced swingarm eligible for

Sportsman and Seventies Two-Stroke/Singles machines only. g) No machine in any category may have more than 7” of front wheel travel and 4” of rear wheel travel, measured at the axle, regardless of original specification. h) All of the following must be covered with rubber and conform with AHRMA competition rules: footpegs, stand mounting lugs, brake rods and anything else that might present a hazard. i) Footpegs must be of the folding type able to pivot upwards and aft at 45-degrees.

j) FORKS: Machines must use OEM or pre-1975 aftermarket forks, with maximum 35mm diameter tubes. Ceriani, Red Wing, Betor or other non-period telescopic forks are not allowed on Dinosaur class machines. No adjustable fork triple clamps are allowed in any class except for OEM adjustable steering stems on

Can-Am and certain period C&J frames. Non-adjustable, billet triple clamps are allowed. k) SHOCKS: No single-shock chassis are permitted. Dual-shock machines may use any shock absorber, providing the technology and design was commercially available in 1974 or was supplied as OEM on any AHRMA-legal dirt track machine. l) ENGINE: No major engine components may be changed or updated to later model parts (e.g., cylinder, head, cases, etc.). Hydraulically-operated clutches are prohibited. m) Machines in all classes may be built to the class limit, plus overbores (in TT racing only, Dinosaur and Classic Open must use the stock displacement, plus overbores). Overbore limits for all classes are as follows: +.080” for singles; +.060” twins; +.040” triples; +.020” fours. Pre-unit Triumph 500 twins may use 650cc crankshaft but must not exceed +.030” overbore.AnyAHRMAofficial may ask for a random engine teardown at any event, without posting the protest fee. Any rider refusing to teardown or found to be using an oversize engine in any

AHRMA competitive event is subject to an immediate 13-month suspension of his/her racing license. n) Two-strokes are limited to no more than two cylinders; multi-cylinder fourstrokes are permitted. Use of compression releases is allowed on any two-stroke machine.All two-strokes must be equipped with an effective silencer. Throttles must be self-closing. All motorcycles must be equipped with a functional handlebar-mounted kill switch. If the motorcycle is equipped with a magneto where an operational kill switch cannot be fitted, then the carburetor settings must be such that a running engine shuts off when the throttle is fully closed. o) CARBURETORS: No flat-slide or injection-type carburetors are allowed.

“Power jet” and “Pumper” type (accelerator pump-equipped) carburetors are not permitted unless such mechanisms are disconnected or removed. Fuel injection is not permitted. Smoothbores with concentric float bowls are not permitted. Period carburetors are encouraged. p) Classic 250 two-strokes are restricted to 32mm for singles, 28mm for twins, except Ossa, which may run the OEM 33mm IRZ carburetor. q) All Dinosaur bikes must use OEM or period-type carburetors with specific exceptions as identified in 10.4.1A.d of the Class C road racing rules. r) All drain plugs must be lockwired. s) All modifications must be consistent with the spirit of the class; period modifications only. t) Appearance and workmanship of a reasonable standard shall be enforced. u) All machines must carry three 10x12-inch (minimum) rectangular number plates—one on the front, and one clearly visible on each side of the motorcycle.

Novice entrants shall have yellow plates, all others must be white. All numbers must be black, at least eight-inches tall, with a minimum one-inch brush stroke.

Any letters must be at least three-inches tall. It is the rider’s responsibility to be scored; legible numbers on the rider’s back and helmet are highly encouraged. All competitors must display their AHRMA-assigned number unless granted prior permission to run a different number at that event only.