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 NOTallowed.
NOTICE: Rules may be frozen for 5 years starting with the 08/09 season subject to review at the 08 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, sandblasting, peening, substitution, or total elimination will not be allowed unless otherwise specified here.
5. Minimum weight is 400 lbs.
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 any material whatsoever allowed. This is include polishing, port matching, deburring, glass or material removal for the purpose 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 for the model pistons, rings and engine gasket are allowed for replacement.
6. Replacing OEM carburetor slide valve and replacement jet components without modification allowed in Formula 500. No modifications to carb 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. Sparkplugs and sparkplug wires and connectors do not have to be OEM.
12. 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.
13. No changes or repairs allowed to the “wye” pipe
14. Engine must remain in the stock location and must use stock engine plate and mounts. Torq links and limiters allowed.
DRIVE
1. Drive clutch must 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 dicsc and track shaft must remain stock and in stock location: no modification or lighting 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 the bulkhead.
5. Must use all original suspension mounting points on chassis and struts
6. May 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 maintain two and one 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 handle bars may be relocated and /or replaced, including extensions, to fit the driver. All ends must be plugged. The handle bars 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 operating mechanism on rear of right handle bar.
TRACK & SKI RUNNER
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 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 lightning.
4. May modify or replace springs. Titanium springs are not allowed.
5. Shocks absorbers must OEM for the model or ISR designated replacements.
6. May remove front shock.
7. May change or add limiters to front and rear of track suspension. No remote limiter adjusters allowed.
8. May relocate rear shock.
9. May add or subtract marginal snow wheels.
10. May add slide rail lube 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 manufacturer. No cutting or other modifications allowed.
3. No welding on hooker 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 modifications allowed. May not lighten fly wheel.
2. Instruments, gauges, and headlights may be removed.
3. Data acquisition and data acquisition systems not allowed.
4. An OEM production taillight, with the brake element on when ever the engine is running is mandatory.
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