No tires may be over 23 x 10.50 x 12 inches in size. Garden tractor type tires. Stock means stock motor on a stock frame. Milled heads are allowed however, see the diagram for specifications. One factory type head gasket installed in the proper location.
Camshaft can be any grind.
Factory stock valve size, intake and exhaust valves need to be O. E. M. stock. Stock flywheel only. Cub style twin disk clutch. Same rules as above in the 0-10 hp. stock class except for the weight. No more than 4000 R.P.M. with R.P.M. stop on block.