- The snowmobile must have original OEM for the model engine, frame and tunnel.
Engine
- Engine components must be OEM for the model unless otherwise specified. May be modified internally, but engine must retain its complete external stock appearance and dimensions.
- Number of cylinders must be OEM for the model. No external fastening devices allowd to secure or hold cylinders in place.
- The cylinders may be raised to change port height. If a plate is used to raise cylinder height, the plate, including gaskets, cannot exceet 1/2 inch (0.50 inch) in thickness.
- Engine may be bored up to class limit. A two percent (2%) overbore allowed. (Example: 700cc engine may be bored up to 714cc’s to run in the 700cc class.)
- Crankshaft and crankcase must be OEM for the model and year. No modification allowd to the external surfaces of the crankcase even if the area is hidden by another part or bracket.
- Cylinder head(s) must be OEM for the model. The cylinder head may be modified internally. The visible outer portion of the cylinder head or cylinder head cover must remain stock appearing, and the spark plug must maintain OEM location.
- Engine components allowable for modification or replacement.
- Bearings
- Rods (rod center to center must remain the same)
- Pistons
- Piston pins
- Rings
- Gaskets
- Reeds and reed blocks may be changed, (external plate may be thicker) if they do not change the outside dimensions of the cylinder or crankcase.
- No external modifications may be made to the crankcase or cylinder to accommodate red block change.
- Carburetors, flanges and intake manifold must be OEM for the brand. Internal modifications are allowed. Carburetor throat may be bored. Intake concept and location must remain OEM for the model.
- On snowmobiles with OEM for the model Electronic Fuel Injection the OEM throttle body, including the exterior, may be modified for increased fuel flow and air. Systems that allow increased fuel delivery and timing may be used (i.e. Power commander or other commercially available). Any sled may use aftermarket ignitions that are commercially available to the public.
- Internal and external modifications may be made to the airbox. The airbox may be removed. Air filters may be used.
- Oil pumps may be removed or disabled. Oil injector nozzles may be removed and plugged. (If oil tank and overflow tank are joined the oil tank must be disabled or the joined tanks removed.)
- Torque arms allowed.
- Rigid motor mounts allowed. OEM for the model engine location must be maintained. Replacing or adding metallic engine mounts is not allowed. Replacing rubber/cushion parts with more rigid parts is allowed.
- Cooling systems must be operational. May contain disconnects for cool down. Heat exchangers may be relocated, modified or removed.
- Any functionally silenced exhaust system allowed. Any commercially available, functionally silenced muffler/stinger must be installed and operational.
- Exhaust outlet must exit downward and rearward. (If OEM exhaust exits behind driver; pipe need not go downward)
- Race Fuel only the use of alcohol, methanol, and nitromethane is prohibited.
Drive
- Any OEM primary and secondary clutch may be used. Roller secondary clutches allowed.
- Primary clutch and secondary clutch may be modified (no RPM limit).
- Jackshafts, of like material and weight, may be changed to accommodate a clutch change. No welding allowed on a jackshaft. Steel and chrome moly allowed. OEM location of shaft must be maintained.
- Any track drive sprocket and non-driving wheels allowed on the track drive axle.
- Track drive axle and chain case must remain OEM for the model and remain in OEM location.
Ski & Track Suspension
- Any aftermarket rear suspension shock may be used, but must resemble the production shock in approximate overall body length, body diameter, and mounting eye overall length.
- Ski stance must be OEM for the model and year.
- Sled must have a minimum ride height of three (3) inches measured at the lowest point of the bulkhead/skid plate. Measurement points to be centered directly in front of the track drive area, (using the spindle centers to determine center point of bulkhead) and must retain 2 inches of remaining compression travel with driver on snowmobile.
- OEM for the brand suspension must be used. Suspension may be moved up and down in the tunnel (limit 3 inches). OEM location must be maintained and may not protrude beyond tunnel configuration.
- Must retain 2 inches of remaining compression travel with driver on snowmobile.
- Any size, material, and number of rear axle idler wheels allowed. Unless specified, no modification to chassis or suspension allowed to accept idler wheels. The rear axle may be moved upward in the slide rails to accept larger rear idler wheels.
- Commercially available long track rails and rail extensions allowed. To facilitate installation of long track rails, suspension may be moved up or down in the tunnel (a limit of three inches). The front torque arm must be OEM stock and located in the stock location on the slide rail. The rear torque arm must remain OEM stock for the model and may be relocated to accommodate the longer track and rail assembly. Suspension components must remain OEM stock for the brand. Tunnel must be extended to accommodate the longer track and suspension.
- No lightweight suspension parts allowed.
- Fox float shocks are allowed in replacement of standar shocks.
Track & Traction
- Any commercially available one-piece molded rubber track allowed.
Skis
- Aftermarket skis allowed. Skis must be commercially available and marketed through normal sales activity. The minimum ski length must be 18 inches. Ski width may not be trimmed. Skis may not be interchanged between brands.
Frame & body
- Any chassis alterations, additions or removals, which alter stock appearance or dimensions are not allowed. Tunnel can be repaired but must maintain OEM length.
- The OEM for model fuel tank cowl must be in place, gallon tank allowed.
- OEM side panels must be used. Lightweight hood is the only lightweight part allowed.
- Headlight assembly may be removed opening must be closed or delete kit installed.
- Taillight must be operational.
