A. Single cylinder engines only are allowed for all classes except twin cylinder engines are allowed for the 250 four stroke class and 4 cylinder engines for 600 class.
B. The sportsman class allows the following engines:
1. Spec 250cc liquid cooled engine
a. The following are the approved engines:
u 1992 to 2001 Honda CR 250cc
n Bore x Stroke: 66.4mm X 72mm
u 2002 to 2007 Honda CR 250cc
n Bore x Stroke: 66.4 mm x 72 mm
b. Cylinder and head must hold a minimum of 20.5cc of fluid for a compression ratio test.
u The volume is measured with the head bolted to the cylinder of a race ready engine, when the piston is at TDC (Top Dead Center) and measured to the top of the spark plug threads.
c. The engine must be stock in configuration and appearance with no internal or performance modifications, other than those modifications listed below: (all other internal or performance modifications will be considered illegal)
1) Any carburetor
2) Any pipe
3) Any fuel pump
4) Any two ringed piston manufactured as an OEM replacement for the approved engine; both rings must be used.
5) Power valves may be removed and replaced with a plug.
6) Clutch linkage and kick-starter assemblies may be removed and plugged.
7) Remove and weld aluminum lug by chain sprocket on engine side case.
8) Remove and weld aluminum casting on case half where carburetor rests.
9) Aftermarket covers may be used for the: clutch cover, ignition and/or power valve.
10) Clutches may be removed and clutch hub may be altered or replaced with an aftermarket hub.
11) Cylinder modifications any internal modifications that do not alter the appearance of the outside of the cylinder.
12) Any Honda straight or angled carb insulator boot.
a) Modifications for carb retention are allowed as long as they do not enhance performance.
13) Stock Honda Head, no inserts.
a) Head cutting is allowed – must meet 20.5cc fluid test.
14) The clutch side may be sealed from the gear case and an additional fill plug may be added.
d.. Additional clarifications:
1) Stock Bore
2) Stock Stroke
3) Stock OEM Crank and Rod, no modifications
4) No base or spacer plates
5) The following stock OEM gaskets must be usedand may not be modified: Head, Base and Reed
a) Only 1 of each gasket may be used and no additional Head, Base or Reed gaskets may be used
6) Ignition must be stock appearing, any plug wire, spark plug or spark plug cap may be used
7) Stock OEM reed cage from a 1992 to 2007 Honda CR250cc model year engine –no modifications
8) No reed spacer
9) No case porting
2. 270cc Air Cooled Engine
a. Engines marketed as an air-cooled 250cc displacement or fewer engine.
b. Maximum piston displacements shall be 270cc
C. There will be only one engine permitted per car.
D. Maximum piston displacements shall be:
Note: To find cubic centimeters (cc) multiply Bore X Bore (mm) x3.14 x stroke (mm) divide by 4000.
E. Titanium cranks are illegal. (Protest able only)