JR. FACTORY STOCK FLAT

Flat Kart Only

Weight: 300 lb.



  • Single cylinder OHV engines only. Clone or Predator 212.
  • Stock engine with a maximum displacement of 212cc.
  • Stock engine with a minimum combustion chamber of 28 cc. To be checked with a CC nut.
  • Stock unaltered cylinder head is required. (All head gaskets are legal).
  • Stock crankshaft unaltered, 2.165” maximum stroke.
  • Unaltered SRI-approved flywheel weighing 3 pounds or more.
  • Stock connecting rod stock length (3.308” max). Billet aluminum is illegal.
  • Stock unaltered piston only (2.766” maximum). Head and piston must be of the same make and model (i.e. Hemi head to Hemi flat top piston, 208 cc piston to 208 cc head, dish piston to wedge head).
  • Stock camshaft cores only, ez-spin assembly must remain as stock. Cam lobe base circle diameter .865 -.005"/+.010". Max intake lift on cam .225"-min .215" lift taken at push rod. Max intake lift at the valve (.261" for Hemi/ .236" for Wedge Head) taken on the valve spring retainer with zero lash. Max exhaust lift on the cam .232"-min .222" lift taken at pushrod. Max exhaust lift at the valve (.267" for Hemi/ .243" for Wedge Head) taken on the valve spring retainer with zero lash. @.050” 230 degree max). Mod 2 Cams not allowed.
  • Stock rocker arms unaltered (Non-Hemi 1:1 ratio max, Hemi 1:1.1 ratio max).
  • Stock lifters, push rods, and valves unaltered.
  • Valve Spring Installed Height Minimum .815 Maximum Spring Tension of 10.8 at a Height of .850 Max Wire Diameter Of .071”.
  • Stock retainers and keepers unaltered.
  • Stock valve cover unaltered. Pulse fitting OK.
  • Stock side cover unaltered. Pulse fitting OK.
  • Stock ignition coil, wire and boot unaltered.
  • Exhaust Requirement:  Any Winnie pipe with minimum length tubing of 5.5” and maximum of 6.5” measured from the surface of the gasket where it meets the head to the end of the threads and maximum OD tubing diameter of .750” measured on the straight section of the pipe, with a +/- .010" tolerance. A transition allowance will be given from the top of the flange up the tube .5" for transition from the stated OD tubing diameter. . Flange thickness will be limited to .5125". RLV Mini 91 Muffler REQUIRED, no alterations to the muffler. The pipe must not be altered to leak via holes in the side of the pipe or gasket.
  • Shoe Clutch only (Any make).
  • Stock blueprinted clone carburetor measuring a maximum .615 at the Venturi and .751” at the exit (Measured with ‘NO-GO’ gauge and a roundness check of venturi. Venturi must be round. No odd shapes. (i.e. egg or ‘D’ shape). You may NOT polish the inside, remove choke or shave butterfly/shaft. Any attempt to draw air past carb will be disqualified.
  • Pump gas only baseline designated by track.
  • Any air filter and/or adapter is legal.
  • Aftermarket carburetor spacers and insulators are illegal.
  • Stock pull start only unaltered.
  • Removal of governor and/or governor components is legal (Plugging holes legal).
  • Removal of oil sensor and/or oil sensor components is legal (Plugging holes legal).
  • Flat kart bodies only.