1. Briggs and Stratton 5 h.p. (13cc) Motorsports motors will be the model of reference.

2. All parts are to remain stock. Any and all parts may be checked against a known stock part.

3. Stock Motorsports cams only. No ground/or twisted cams.

4. #5 Carburetor only, as cast from the factory. Carb saver brackets are allowed.

5. No modifications to the throttle shaft.

6. Specified Pipe and Muffler combination must be used. Pipe to be a Robertson #1-MC. Muffler to be RLV #8-91 (1 5/16"). Mufflers must be mounted with an approved muffler clamp. Welding of mufflers to headers is prohibited.

7. Spark plug is a non-tech item.

8. Jet size is a non-tech item.

9. Recoil may or may not be mounted to the motor.

10. Stock flywheel only. No modifications. 

11. Stock flywheel key to be installed in the stock position. No advanced timing.

12. No decking of the block. Must be the original factory finish. 

13. No modifications to the fuel tank or the shroud. Pressure fuel tanks not allowed.

14. Approved chain guard must be in place during all events.

15. No blueprinting of the head.

16. Pure methanol only. No additives.

17. Stock crankcase breather only. Overflow catch cans are mandatory and tubing must run from the breather to the catch can only.

18. Intake and Exhaust settings per the factory service manuals. Intake (.005-.007) Exhaust (.009-.011)

19. Piston may be oversize. Max .035 piston.

20. Stroke 2.427-2.447. Stock rods only. No undersize rods allowed.

21. Crankshaft to remain stock. No balancing, lightening, polishing, or reworking. (.990 min.)

22. Stock valves, seats, springs, lifters, and angles. Intake 30 degrees, exhaust 45 degrees. One angle only.

23. Minimum head gasket thickness to be checked between head bolts is .043. Briggs gasket only.

24. Stock class air filter adapter.

25. Restrictors to be installed between the block and the carburetor. One gasket is required on each side of the plate. When the plate is installed correctly the Horstman logo is clearly visible above the carburetor. Junior/Rookie Box Stock to run .425 (purple). 

26. All motors are subject to a $600 claim.

27. All clutches are subject to a $70 claim.

28. Claims are open to competitors only . All claims are to be made within 15 minutes of the conclusion of the last event of the day for the class to be claimed. All claims will be brought to the attention of the race director immediately.

29. Tires are to be Burris 33A  Series tires only.

30. Clutch's shall be either Noram GE series or Premier Magnum steel shoe clutch's only. All clutch's subject to claim as above.  

All engines are subject to pre-inspection and MUST be sealed. All motors may be subject to inspection pre or post race. Track officials reserve the right to exchange motors/components with any competitor in these divisions with a known stock Motorsports motor/component pre race for that competitor to use for that day/race. Track officials reserve the right to ask any competitor to move up in divisions at any time during the race season. This class is designed to be fun and inexpensive.

*Box Stock will be also running a SEALED Animal (6.5) OHV motor for 2010 and beyond.