Formula 500

FORMULA 500

Snowmobiles in this class must be built to resemble a Sprint or Champ snowmobile from any of the current brands.
In stock and stock based classes, no change or modification is allowed unless specifically allowed by these rules.  If these rules do not specifically allow a change or modification, then it must be assumed that the change or modification is not allowed.
NOTICE: Rules may be frozen for 5 years starting with the 09-10 season subject to review at the 09 rules meeting.
GENERAL RULES

  1. Snowmobile must comply with the GENERAL RULES AND REGULATIONS.
  2. The snowmobile must originate from 1989-1992 Polaris Indy 500 carbureted model.
  3. The brand of hood, engine and logo need not match. 
  4. Removal of any material from total snowmobile by means of heat, acid, drilling, grinding, sand blasting, peening, substitution, or total elimination will not be allowed unless otherwise specified here.
  5. Minimum weight is 400 pounds.
  6. Maximum overall width of sled is 45 inches.

ENGINE

  1. No component of the engine may be altered, changed or enlarged from the engine manufacturer’s original stock specifications, nor         may any additional components be added to the engine.  No engine kits allowed.
  2. Blueprinting is not allowed. No removal of material whatsoever allowed. This is to include polishing, port matching, deburring, glass or sand blasting surfaces or material removal for the purposes of engine balancing or other reasons.
  3. No changes in engine dimensions can be made by gasket adjustments.  Gaskets may be trimmed but must remain OEM and OEM thickness.
  4. Maximum cylinder overbore for wear or cylinder repair cannot exceed .020 inch.
  5. OEM for the model and Kimpex or SPI for the model pistons, rings and engine gaskets are allowed for replacement.
  6. Replacing OEM carburetor slide valve and replacement jet components without modification allowed in FORMULA 500.  No modification to carburetor body allowed.
  7. No additional fuel pumps may be added.
  8. Air box and oil injection system may be removed.
  9. Thermostat may be removed.
  10. Cooling system must remain completely stock and in the OEM location.
  11. Spark plugs, spark plug wires and connectors do not have to be OEM.
  1. The exhaust system must be OEM for the model and be mounted in the OEM location for the model.  Welded-on after muffler and internal stinger pipe may be removed and replaced with any size stinger.  The exhaust system must be functionally silenced.  The ball socket on exhaust chamber may be repaired or replaced but MUST maintain original tuned length and inside diameter.  NO OTHER CHANGES ALLOWED.  
  2. No changes or repairs allowed to "Y" pipe.
  3. Engine must remain in stock location and must use stock engine plate and mounts.  Torque limiters allowed.

drive

  1. Drive clutch must be P-85 Polaris.
  2. Any commercially available driven clutch and internal components allowed.
  3. Clutches and components may be modified.
  4. Chain case, jackshaft, brake disc and track shaft must remain stock and in stock location; no modifications or lightening allowed.  Chain and sprocket ratio may be changed.  Belt drive system is not allowed.
  5. Brake cooling duct, inside the hood, is allowed.

ski suspension & steering

  1. Ski suspension and steering must be OEM for the model unless otherwise specified.
  2. Radius rods and tie rods may be replaced or modified.
  3. Maximum outside to outside width across the skis is 45 inches.
  4. Maximum total offset allowed is 1 inch, measured from the center of bulkhead.  EXAMPLE: 23 inches from the center of bulkhead to the outside right ski and 22 inches from center of bulkhead to the outside left ski = 45 inches outside ski stance with 1 inch total offset.
  5. Must use all original suspension mounting points on chassis and struts.
  6. May use any spring or spring adjusters.  Titanium springs are not allowed.
  7. POLARIS part # 7041144 is the only ski shock allowed.  Shock absorbers must be OEM for the model or ISR designated replacements.
  8. Sway bars may be replaced but must fit in stock location thru bulkhead.
  9. Limiter strap allowed, but must maintain two and a half (2.5) inches of usable downward travel with the driver seated.  Travel measured at the front bumper.
  10. Suspension components may be reinforced but no geometry changes are allowed except camber.
  11. The steering column and handlebars may be relocated and/or replaced.  Extensions may be added to suit the driver.  The lower end of the steering column must be secured with a minimum of 4 bolts. One of the 4 bolts must be in one of the OEM mounting holes.  The handlebar and column material must be of same as the OEM material with the same wall thickness (or greater) and tubing outside diameter as the OEM components. The use of a universal joint is not allowed.
  12. Throttle lever may be replaced but must be thumb operated with a direct mechanical operated mechanism on rear side of right handlebar.

 

skis & ski runner

  1. OEM (for the brand) or aftermarket skis allowed.  Must conform to General Competition Rules.  Ski mount on spindle may be narrowed to allow ski mounting.
  2. Minimum flat length of ski bottom is 14 inches.  Minimum ski width is 3 1/4 inches.
  3. Reinforcement is allowed on the top of the ski board only.
  4. Maximum carbide length is 6 inches per ski.  Must be one continuous cutting edge with no other sharp edges on the ski.

track suspension

  1. Complete track suspension and components MUST be OEM stock for the model unless otherwise specified.
  2. Track suspension must maintain a minimum of 2 inches of useable, vertical travel with the driver seated.
  3. May drill new holes in tunnel or rail to change mounting locations.  May not drill excessive amount of holes for lightening.
  4. May modify or replace springs.  Titanium springs are not allowed.
  5. Shock absorbers must be OEM for the model or ISR designated replacements.
  6. May remove front shock.
  7. May relocate rear shock.
  8. May change or add limiters to front and rear of track suspension.  No remote limiter adjusters allowed.
  9. May add or subtract marginal snow wheels and their mounts.
  10. May add slide lubrication system.

track & traction

  1. Any commercially available 121-inch by 15 inch is allowed.  Minimum track lug height is 0.50 inch.
  2. The track must be used as produced by the molder of the track.  No cutting or other modifications allowed.
  3. No weld on hooker's plates.
  4. No studs allowed directly under rails.
  5. Traction products must conform to Oval Sprint requirements.

frame & body

  1. Must use 1989-1992 Polaris Indy 500.
  2. Chassis may be reinforced.
  3. May alter or replace hood, windshield, belly pan, seat, fuel tank and foot stirrups.
  4. May remove bumpers, dash panels, oil tank, lights and wiring.

ignition & electrical

  1. Ignition system MUST be OEM stock for this engine, no modification allowed.  May not lighten flywheel.
  2. Instruments, gauges and headlight may be removed.
  3. Data acquisition and data acquisition systems not allowed.
  4. An approved LED taillight must be illuminated whenever the snowmobile is on the racing surface, whether the engine is running or not.

 

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