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Pro Mod Class Rules
This is only a summary of the rules. For complete rules see ISR rule book. It is highly recommended that racers considering the Pro Mod class obtain a current copy of the rule book. Pro Mod is bascially the same as the previous Pro Stock class but 3 cylinder engines from the same manufacturer are allowed in a chassis that originally only had a 2 cylinder.
No modification allowed unless specifically allowed by ISR rules. If those rules do not spefically allow a change or modification, then it must be assumed that the change or modification is not allowed.
Minimum combined weights (sled and rider) for all sanctioned classes: 625 lbs (550 for 2 cylinder engine)
Sleds must have stab wheels and clutch cover. See main Rules page for diagrams.
Engines must be OEM for the brand. No swapping between brands allowed. Triple cyinder engines may be installed in twin cylinder chassis.
Cylinders may be modified internally but must be OEM for the brand with no external changes allowed. Cylinder heads must be OEM for the brand but may be modified internally including changing replaceable combustion chambers. The visible outer portion of the cylinder head or cylinder head cover must remain stock appearing. Cylinder, crankcase, crankshaft, and heads may be swapped within the brand.
Cylinders may be bored up or sleeved down to any size but will change snowmobile class. For example, a 600 cc engine may not be bored to 800 cc's and still run in the 600 cc class. It can however be run in the 800 cc class.
Any carburator may be used.
Traction devices (studs or picks) are allowed. Sleds running traction products must use rear tunnel enclosure (see main rules page for diagram). Track lug timming is allowed to a minimum height of .5".
Commercially available long track kits are allowed. Kit must be used in its entirety. Any track suspension allowed that can be installed within the confines of the tunnel. Race director will inspect for structural integrity. Must be a minimum of 2" of remaining compression travel with driver on snowmobile.
OEM appearing for the model hood, seat and fuel tank must be used. The fuel tank may be modified to accomodate a fuel cell but must retain its OEM outer appearance
No modification allowed unless specifically allowed by ISR rules. If those rules do not spefically allow a change or modification, then it must be assumed that the change or modification is not allowed.
Minimum combined weights (sled and rider) for all sanctioned classes: 625 lbs (550 for 2 cylinder engine)
Sleds must have stab wheels and clutch cover. See main Rules page for diagrams.
Engines must be OEM for the brand. No swapping between brands allowed. Triple cyinder engines may be installed in twin cylinder chassis.
Cylinders may be modified internally but must be OEM for the brand with no external changes allowed. Cylinder heads must be OEM for the brand but may be modified internally including changing replaceable combustion chambers. The visible outer portion of the cylinder head or cylinder head cover must remain stock appearing. Cylinder, crankcase, crankshaft, and heads may be swapped within the brand.
Cylinders may be bored up or sleeved down to any size but will change snowmobile class. For example, a 600 cc engine may not be bored to 800 cc's and still run in the 600 cc class. It can however be run in the 800 cc class.
Any carburator may be used.
Traction devices (studs or picks) are allowed. Sleds running traction products must use rear tunnel enclosure (see main rules page for diagram). Track lug timming is allowed to a minimum height of .5".
Commercially available long track kits are allowed. Kit must be used in its entirety. Any track suspension allowed that can be installed within the confines of the tunnel. Race director will inspect for structural integrity. Must be a minimum of 2" of remaining compression travel with driver on snowmobile.
OEM appearing for the model hood, seat and fuel tank must be used. The fuel tank may be modified to accomodate a fuel cell but must retain its OEM outer appearance