MIDWEST INTERNATIONAL RACING ASSOCIATION

GENERAL SNOWMOBILE REQUIEMENTS

Notice: Effective 1 June 09, titanium parts will not be allowed in Vintage Oval Racing.

DRIVE

1. (Mandatory in all classes except stock and super stock where it is recommended.) The clutch cover must conform to the rules for Modified Oval Sprint classes

SKI SUSPENSION AND STEERING

1. Leaf spring snowmobiles must have functional steel leaf springs.
2. Springs must be steel or OEM for the model if some other material.
3. In all classes: Offset ski stance not allowed unless produced by the OEM for the model.
4. All ISF snowmobiles must have a minimum of two (2) inches of compression travel with the rider on the snowmobile. Travel measured at bumper.

TRACK SUSPENSION

1. All ISF snowmobiles must have a minimum of two (2) inches of compression travel with the rider on the snowmobile. Travel measured at bumper.
2. Springs must be steel or OEM for the model if other material.

TRACK AND TRACTION

1. No cleated tracks allowed
2. Traction devices must conform to Oval sprint rules.

FRAME AND BODY

1. Engine, chassis and components ID numbers should be maintained. But are not required as in Oval Sprint.
2. Maximum overall width of any snowmobile is 45 inches (outside of skis or body, whichever is wider)

IGNITION AND ELECTRICAL

1. Programmable ignition systems allowed in all classes. Ignition reprogramming is not allowed in the staging area or on the racetrack.
2. Any OEM production taillight, with the brake element on whenever the engine is running is mandatory.

340 STOCK AIRCOOLED SINGLE CYLINDER

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.

1. Stock qualified, Leaf Spring Model 1985 or older is eligible. No limited production or race only models (such as 76 and 77 Yamaha SRX, mercury snow twister, Ski Doo Blizzard, Arctic Any cat Z or EXT)

ENGINE

1. The engine must be OEM for the model.
2. Engine, engine mounts and exhaust must remain in original OEM for the model locations (of the chassis).
3. Any internal modifications allowed to the Engine.
4. No external modifications allowed. Engine must maintain OEM for the model appearance.
5. Engine bore size may be increased up to the class limit.
6. Aftermarket pistons allowed
7. OEM intake concept(for the engine) must be maintained( i.e. piston port, reed valve, ect)
8. Any round slide carburetor from a stock qualified snowmobile is allowed. Flat slide carburetors not allowed. Air intake silencers (air boxes) may be removed.
9. Cooling system concept (for the engine) must be maintained and fully functioning (i.e. free air, fan cooled)
10. Must be naturally aspirated.
11. OEM for the model exhaust system must be used.

DRIVE

1. Any snowmobile brand OEM primary clutch allowed
2. Secondary clutch must be OEM for the model chassis.
3. Chain case must be OEM
4. Chain case may be moved up to two inches.
5. Any track drive shaft and track drive sprockets may be used.
6. Track drive shaft may be relocated a maximum distance of two inches.
7. For chassis without jackshaft, a jackshaft may not be added.
8. Jackshaft models must use OEM for the model jackshaft.
9. Brake components may be replaced. Must be commercially available and not modified

SKI SUSPENSION AND STEERING

1. Ski must OEM for the model or an after market replacement.
2. Leaf springs must be steel and functional.
3. Ski spreaders allowed. Maximum increase 3 inches (each ski).
4. Only oil filled shocks can be used on the skis (no gas shocks).
5. Spindles must be enclosed.
6. No cobra skis allowed.
7. Steering column must be OEM for the model chassis. The handlebars and/or handlebar mounting bracket may be replaced.
8. Any commercially available handlebar allowed.

TRACK SUSPENSION

1. Any track suspension from a stock qualified 1985 or older model is allowed.

TRACK AND TRACTION

1. Ant commercially available one-piece molded rubber track allowed. Track must fit within the confines of the tunnel without modification to the track.
2. The track must be used as produced by the molder of the track. No cutting or other modifications allowed.

FRAME AND BODY

1. Frame must be OEM for the brand.
2. No modifications allowed to frame.
3. Hood must be OEM for the model.
4. Windshield may be modified, replaced or removed.
5. Headlight must be taped.
6. Fuel tank must OEM for the model or an aftermarket replacement.
7. Seat must maintain OEM contour and stock appearance for the model. Minimum seat thickness is 3 inches.