Tractor Design Rules

General Tractor Design Rules

  1.  All tractors must have functional brakes, steering wheel, secure seat with a minimum 3” backrest, hood, grill, wheel fenders and a securely fastened exhaust.
  2. All tractors must have a break away kill switch, with a sturdy ring 1 ½” in diameter, mounted at the rear of the tractor and easily accessible. Kill switch must immediately kill the engine and power to the electric fuel pump.
  3. Must Have “dead-man” style throttle. Engine throttle must return to idle when the driver pressure is released. Gas pedal recommended but not required.
  4. Shifting is not allowed.
  5. Gasoline, racing gasoline or E85 only. No alcohol type fuel is allowed. No additives of any kind. No nitrous oxide or compressed gas of any kind.
  6. Batteries and fuel tanks must be mounted securely.
  7. Fuel pumps are allowed (mechanical or electrical).
  8. All drive belts/chains must be shielded radially, top, front and rear with 1/16” steel. Shield must be wider than the belt.
  9. All exhaust must discharge vertically +/- 10 degree; exceptions to this rule would be the use of stock mufflers or use of rear engine tractors.
  10. All ignition points must be covered to protect from chance of fire.
  11. All weights must be securely mounted on stationary weight brackets.
  12. All tractors must have adequate stabilizer bars to prevent rear tip over, wheels are allowed, must be strong enough to support the tractor and driver at pulling weight. Wheels or pad must be at least 5” behind rear tires and not more than 5” off the ground. Use of bump bars is recommended. Stabilizer bars cannot interfere with hitch.
  13. All tractors must have a stationary hitch not more than 13 “off the ground. Must have a minimum of a 1 ½” hole in diameter.
  14. 1 ½” hole must be no more than 3⁄4” from the rear of the hitch material.
  15. Maximum length of 8 feet (96”) from the center of the rear axle to the farthest point forward.
  16. Tractors must use an OEM garden tractor rear end housing.
  17. Flathead, OHV or Twin engines allowed.
  18. Must use stock appearing tractor style carburetor. NO motorcycle carbs.
  19. Fuel injection is allowed, the throttle body to be no larger than 1 ¼” in diameter.
  20. Engine block must be factory OEM production or OEM replacement.
  21. Must have a factory head bolt pattern.
  22. Billet heads are allowed on flathead engines.
  23. Porting and polishing allowed.
  24. NO reverse port engines allowed.
  25. Maximum rear tire size of 26x12x12. No dual wheels or chains.
  26. All clutch assemblies and flywheel must be fully surrounded by minimum sheet metal, 1/16” steel or 3/16” aluminum (or equivalent).

Sportsman Design Rules

  1.  Must comply with ALL “General Tractor Design Rules”.
  2. Maximum of two cylinders (can be two single, OEM hp ratings will be added together to determine class) cannot exceed 8hp.
  3. Engine RPM is considered unlimited/open.
  4. For engines not running a function governor
    1. Must have a cylinder head strapping device that will retain the head within the tractor in the event of engine failure.
    2. Must have a 3/16” steel or 1/4“ aluminum plate on the connecting rod “thrust” side of the engine to retain or redirect any debris that may result from an engine failure.

Pro Stock Design Rules

  1. Must comply with ALL “General Tractor Design Rules”.
  2. Maximum of two cylinders (can be two single, OEM hp ratings will be added together to determine class) cannot exceed 16hp.
  3. Engine RPM must not exceed 4,000 RPM, tested at full throttle with no load. A digital tachometer will be used to determine RPM. RPM will be verified at the start of season and may be spot checked as Two Rivers GTPA officials see fit.

Top Eliminator Design Rules

  1.  Must comply with ALL “General Tractor Design Rules”.
  2. Maximum of two cylinders (can be two single, OEM hp ratings will be added together to determine class) cannot exceed 16hp.
  3. Engine RPM is considered unlimited/open.
  4. Must have a cylinder head strapping device that will retain the head within the tractor in the event of engine failure.
  5. Must have a 3/16” steel or 1/4" aluminum plate on the connecting rod “thrust” side of the engine to retain or redirect any debris that may result from an engine failure.

V-Twin Design Rules

  1.  Must comply with ALL “General Tractor Design Rules”.
  2. Maximum of two cylinders (can be two single, OEM hp ratings will be added together to determine class) cannot exceed 25hp.
  3. Frame may be altered to accept a non-original engine.
  4. No welding or modifying of block or cylinder head. Cylinder head must maintain stock combustion chamber. Copper head gasket allowed.
  5. Maximum bore size .50mm over manufacturer's standard specifications. Pistons must not protrude out of the cylinder more than .005”.
  6. No fabricated manifolds, carburetor stand offs, spacers are allowed. Velocity stacks are allowed.
  7. Carburetor must be stock, unaltered and unpolished. Choke butterfly and shaft can be removed. Air restricting venture must not exceed stock size for model, horsepower, and configuration. Carb may have an adjustable main jet. 
  8. Billet steel or aluminum flywheels are allowed. No welding or machining of cast flywheels.
  9. Adjustable steel flywheels allowed can’t exceed 32 pound weight limit. Pulley weight not to exceed 15 pounds. Total weight of flywheel and pulley not to exceed 32 pounds.
  10. Reground cams allowed, with a maximum lift of .245 lift at the cam, open duration and must run stock valve train.
  11. Engine RPM must not exceed 4250 RPM, tested at full throttle with no load. A digital tachometer will be used to determine RPM. RPM will be verified at the start of season and may be spot checked as Two Rivers GTPA officials see fit.