Marion County Speedway Mini Sprint Rules
The Mini/Micro Sprint car will consist of four wheels, open cockpit, open wheel, single seat, and full suspension with Midget or Sprint car style hood and tail. The engine shall be located in the front of the vehicle.
The chassis must be at least a six-point roll cage and must be a minimum diameter of one (1) inch, with a minimum tubing thickness of .o95″ for mild steel (ERW or DOM). The tubing minimum thickness for chrome-moly, for one (1) inch shall be .083″. For cars made from larger tubing, the tubing thickness may drop one (1) gauge for each diameter greater than one (1) inch. Vehicles must have elbow bars between front and rear uprights. Bumpers and nerf bars may have a minimum diameter of 3/4″ inch and maximum diameter of 1″ and must not extend beyond the outside edge of the vehicles tires. The use of conduit is prohibited. The space between the top tubes of the roll cage and the seated drive’s helmet must beat least 3″. The rear push bar the extends horizontally down the back must be bent to reconnect with the car, or sawed off and sanded until smooth.
The drivers are allowed in-cockpit adjustments. All other adjustments must be verified by officials. If in doubt ask an Official before event. The Mini-Sprint wing span can be a maximum of 14 sq. ft. No wooden construction is permitted. No nerf wing. Sheeting is not allowed.
Front suspension may be coil-over or torsion bars; rear suspension may also be coil-over or torsion bars.
Diameter maximum -10″ rims only permitted. A bead lock right rear is mandatory equipment. A maximum of 14″ wheel width (15 inches as measured from outside to outside of wheel) is allowed.
Right rear tire must be a 50-durometer reading or harder in a 10″ diameter tire before and 15 minutes after the event. All other tires can be any compounds. No tire treating of any type is allowed. No bleeder valves allowed. Any brand of tires can be used.
Drives must be chain driven only. No quick-change box, or belt drives will be allowed.
Wheelbase must be a minimum of 58″ with a maximum of 72″. Maximum width of rear axle is 54″.
Minimum weight with the driver shall be:
Weights may be added to make minimum weight limit and must be solid material. The weights MUST be securely fastened. A 2-point securing system is mandatory to prevent weight loss.
Car number must be permanently engraved on all weights and bright color painted.
Any four-stroke motorcycle engine sold in the USA or Canada meeting EPA certification and OEM stock, up to and including 750cc will be allowed. The engine must be in production for one full year or in the second year of production UP TO 2012. Engine must be stock bore and stroke for that specific model engine. Example: 600cc Yamaha, Suzuki, Kawasaki, Honda, 636cc Kawasaki RR, 750cc Suzuki. All Factory stamping of motors must be present and not removed or altered to prevent the use of illegally obtained motors. If altered must have receipt where motor was purchased by next race. Muffler is mandatory and must be securely fastened. Exhaust system may not enter the driver’s compartment. Side cover and clutch cover may be after market in the interest of engine protection. All engine firewall must be a min. 1/16″ thickness aluminum or steel. Center mounted engine firewall must be located from top of back engine case to bottom frame rail. Side-mounted engine firewall must be located from the top of the engine-case to bottom frame rail, and 10″ in front of the right side of engine.
The only engine modification permitted is the modification of the oil pan, and degree of cams. Slotted cam gears, after market clutch parts, fuel injectors, fuel rail and any ignitions modifications are allowed. NO OTHER MODIFICATION IS PERMITTED. THERE WILL BE NO PORTING;POLISHING OF THE INTAKE OR EXHAUST RUNNERS, NO REMOVING OF ANY METAL FROM THE ENGINE. No bore or stroke modifications allowed. Engine must be stock bore and stroke for that specific model engine. THERE WILL BE NO POLISHING OF THE COMBUSTION CHAMBER. NO EXTERNAL MAGS ALLOWED No removing or metal from crankshaft and/or connecting rods. No cams other than OEM stock specifications allowed for the year engine. Part #’s must match. No regrinding of cams.
Maximum of 41mm re-jetting is permitted. After market flat-side carburetors are allowed. No turbo chargers or superchargers, traction control allowed. Electronic fuel injection is allowed. After market fuel injectors and furl rails are allowed with alcohol. Must have high-pressure fuel injection gas lines. No after market throttle bodies or mechanical fuel injection are allowed (FORBIDDEN). Throttle bodies must be OEM.
Fuel and Oil
Any racing gas/pump gas, alcohol/methanol are allowed. Car must have approved racing fuel cell, with or without bladder.
Must be stock OEM. All gears must be all in place and functioning, subject to inspection.
Starter must operate. Car must be capable of leaving the pits.
No radios are allowed except for race receive