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FORMULA 500 - Rules
The Fastest Growing Class in Oval Racing
FORMULA 500, NO CHANGE OR MODIFICATION CAN BE DONE TO THE STOCK QUALIFIED
SNOWMOBILE 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.
THESE SLEDS WILL BE BUILT TO RESEMBLE A SPRINT OR CHAMP SNOWMOBILE OF ANY
OF THE CURRENT BRANDS.
GENERAL RULES
1. Snowmobile must comply with the GENERAL RULES AND REGULATIONS section.
2. The sled must originate from 1989-1992 Polaris Indy 500 carb. model.
3. The brand of hood, engine and logo need not match.
4. Removal of any material from total machine by means of heat, acid, drilling, grinding,
sand blasting, peening, substitution, or total elimination will not be allowed unless otherwise
specified in this section.
5. Minimum weight is 415 pounds.
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 will be 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 inches
(1/2mm).
5. Stock OEM pistons only are allowed for replacement.
6. OEM carburetor slide valve and replacement jet components without modification will be
allowed in FORMULA 500. No modification to carb body will be 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. 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.
12. No changes or repairs allowed to "Y" pipe.
13. Engine must remain in stock location and must use stock engine plate and mounts.
Torque limiters allowed.
DRIVE
1. Drive Clutch Must Be Stock P-85. Any commercially available driven clutches and internal
components may be used. Clutches and components may be modified.
2. 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.
3. 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 ski stance is 45 inches measured on the outside of the skis.
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.
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, including
extensions, to fit the driver. All ends must be plugged (see diagram in GENERAL COMP.
SECTION). The handlebar must be of the same material with the same wall thickness (or
greater) and tubing outside diameter.
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. May not use more than a 6 inches long sharp
edge of any kind per 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. May remove front shock.
6. May relocate rear shock.
7. May change or add limiters to front and rear of track suspension. No remote limiter
adjusters allowed.
8. May add or subtract marginal snow wheels and their mounts.
9. May add slide lubers.
TRACK & TRACTION
1. MUST use OEM stock track for the model 121 inches x 15 inches or Camoplast # 9812 R.
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. Any brand RED taillight is allowed but must have 1157 bulb with brake element illuminated
whenever engine is running.
3. Instruments, gauges and headlight may be altered, removed or replaced.
4. Spark plugs, spark plug wires and connectors do not have to be OEM.
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