FORMULA 500 (2008 rules)
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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 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.
GENERAL RULES |
GENERAL RULES
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1.
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Snowmobile must comply with the GENERAL RULES AND REGULATIONS section. |
2.
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The sled must originate from 1989-1992 Polaris Indy 500 carburated model. |
3.
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The brand of hood, engine and logo need not match. |
4.
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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 in this section. |
5.
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Minimum weight is 400 pounds. |
6.
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On board data acquisition system is not allowed in the FORMULA 500 class. (This includes memory tach). |
ENGINE
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1.
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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.
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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.
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No changes in engine dimensions can be made by gasket adjustments. Gaskets may be trimmed but must remain OEM and OEM thickness. KIMPEX gasket set part # 09-712185A & SPI gasket set part # G5005 may be used. |
4.
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Maximum cylinder overbore for wear or cylinder repair cannot exceed .020 inches (1/2mm). |
5.
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Stock OEM pistons are allowed for replacement. The following replacement pistons are allowed:
Pistons KIMPEX standard 09-711
Pistons KIMPEX .010 09-711-01
Pistons KIMPEX .020 09-711-02
Pistons SPI standard 9712PS
Pistons SPI .010 9712P1
Pistons SPI .020 9712P2 |
6.
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Replacing OEM carburetor slide valve and replacement jet components without modification allowed in FORMULA 500. No modification to carb body allowed. |
7.
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No additional fuel pumps may be added. |
8.
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Air box and oil injection system may be removed. |
9.
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Thermostat may be removed. |
10.
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Cooling system must remain completely stock and in the OEM location . |
11.
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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.
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No changes or repairs allowed to “Y” pipe. |
13.
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Engine must remain in stock location and must use stock engine plate and mounts. Torque limiters allowed. |
DRIVE
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1.
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The primary clutch must be a POLARIS drive clutch, model P-85. No machining, grinding, cutting or welding allowed on the clutch. Any combination of springs, weights, ramps may be used. Metal may be removed but not added to ramps or flyweights in the primary clutch. |
2.
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Any driven clutch may be used. Driven clutch and components may be modified. |
3.
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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. |
4.
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Brake cooling duct, inside the hood, is allowed. |
SKI SUSPENSION AND STEERING
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1.
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Ski suspension and steering must be OEM for the model unless otherwise specified. |
2.
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Radius rods and tie rods may be replaced or modified. |
3.
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Maximum outside to outside width across the skis is 45 inches. |
4.
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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.
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Must use all original suspension mounting points on chassis and struts. |
6.
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May use any spring or spring adjusters. Titanium springs are not allowed. |
7.
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POLARIS part # 7041144 is the only OEM ski shock allowed. KIMPEX part # 08-113 is the only replacement ski shock allowed. |
8.
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Sway bars may be replaced but must fit in stock location thru bulkhead. |
9.
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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.
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Suspension components may be reinforced but no geometry changes are allowed except camber. |
11.
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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.
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Throttle lever may be replaced but must be thumb operated with a direct mechanical operated mechanism on rear side of right handlebar. |
SKIS AND SKI RUNNER
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1.
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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.
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Minimum flat length of ski bottom is 14 inches. Minimum ski width is 3 1/4 inches. |
3.
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Reinforcement is allowed on the top of the ski board only. |
4.
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Maximum carbide length is 6 inches per ski. Must be one continuous cutting edge with no other sharp edges on the ski. |
TRACK SUSPENSION
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1.
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Complete track suspension and components MUST be OEM stock for the model unless otherwise specified. |
2.
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Track suspension must maintain a minimum of 2 inches of useable, vertical travel with the driver seated. |
3.
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May drill new holes in tunnel or rail to change mounting locations. May not drill excessive amount of holes for lightening. |
4.
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May modify or replace springs. Titanium springs are not allowed. |
5.
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POLARIS part # 7041142 is the only OEM front shock of the rear suspension allowed. KIMPEX part # 04-271 is the only replacement front shock of the rear suspension allowed. |
6.
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May remove front shock. |
7.
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POLARIS part # 7041250 is the only OEM rear shock of the rear suspension allowed. KIMPEX part # 04-235 is the only replacement rear shock of the rear suspension allowed. |
8.
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May relocate rear shock. |
9.
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May change or add limiters to front and rear of track suspension. No remote limiter adjusters allowed. |
10.
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May add or subtract marginal snow wheels and their mounts. |
11.
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May add slide lubrication system. |
TRACK AND TRACTION
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1.
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Any commercially available rubber track 121 inches x 15 inches is allowed. Minimum track lug height is .50 inch. |
2.
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The track must be used as produced by the molder of the track. No cutting or other modifications allowed. |
3.
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No weld on hooker's plates. |
4.
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No studs allowed directly under rails. |
5.
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Traction products must conform to Oval Sprint requirements. |
FRAME AND BODY
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1.
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Must use 1989-1992 Polaris Indy 500. |
2.
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Chassis may be reinforced. |
3.
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May alter or replace hood, windshield, belly pan, seat, fuel tank and foot stirrups. |
4.
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May remove bumpers, dash panels, oil tank, lights and wiring. |
IGNITION AND ELECTRICAL
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1.
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Ignition system MUST be OEM stock for this engine, no modification allowed. May not lighten flywheel. |
2.
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Any OEM snowmobile taillight is allowed but must have 1157 bulb with brake element illuminated whenever engine is running. |
3.
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Instruments, gauges and headlight may be removed. |
4.
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Spark plugs, spark plug wires and connector not have to be OEM. |
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