Snow and Grass Drag Improved Stock Class Rules
This is only a summary of the rules. For complete rules see ISR rule book.
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. Changes allowed in stock are allowed in Improved Stock.
Minimum combined weights (sled and rider):
Improved Stock 600 - 700 lbs (645 for 2 cylinder engine)
Improved Stock 700 - 750 lbs (695 for 2 cylinder engine)
Improved Stock 800 & 1000 - 775 (685 for 2 cylinder engine)
Sleds moving to higher displacement classes will not be required to meet the minimum weight for that class.
Sleds must have stab wheels and clutch cover. See main Rules page for diagrams.
Cylinders may be modified internally but must be OEM for the model with no external changes allowed. Cylinder heads must be OEM for the model 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. Exception is Improved Stock 1000 where aftermarket cylinders and heads are allowed.
Any functionaly silenced exhaust is allowed.
Cylinders may only be bored up to class limit. Example, a 670 cc engine may be bored up to 700 cc's but may not be bored up to 800 cc's to run in the 800 cc class. Exception is the 1000 cc improved class where any engine may be over-bored up to the class limit.
Airbox may be modified or removed. Flywheel harmonic balancer may not be removed. Any clutches allowed.
Traction devices (studs or picks) are not allowed on snow but are allowed on grass. Track cutting or trimming is not allowed.
Commercially available long track kits are allowed. Kit must be used in its entirety. Race director will inspect for structural integrity.
Any size, material, and number of rear axle idler wheels allowed. Rear axle may be moved upward in the slide rails to accept larger idler wheels.
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. Changes allowed in stock are allowed in Improved Stock.
Minimum combined weights (sled and rider):
Improved Stock 600 - 700 lbs (645 for 2 cylinder engine)
Improved Stock 700 - 750 lbs (695 for 2 cylinder engine)
Improved Stock 800 & 1000 - 775 (685 for 2 cylinder engine)
Sleds moving to higher displacement classes will not be required to meet the minimum weight for that class.
Sleds must have stab wheels and clutch cover. See main Rules page for diagrams.
Cylinders may be modified internally but must be OEM for the model with no external changes allowed. Cylinder heads must be OEM for the model 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. Exception is Improved Stock 1000 where aftermarket cylinders and heads are allowed.
Any functionaly silenced exhaust is allowed.
Cylinders may only be bored up to class limit. Example, a 670 cc engine may be bored up to 700 cc's but may not be bored up to 800 cc's to run in the 800 cc class. Exception is the 1000 cc improved class where any engine may be over-bored up to the class limit.
Airbox may be modified or removed. Flywheel harmonic balancer may not be removed. Any clutches allowed.
Traction devices (studs or picks) are not allowed on snow but are allowed on grass. Track cutting or trimming is not allowed.
Commercially available long track kits are allowed. Kit must be used in its entirety. Race director will inspect for structural integrity.
Any size, material, and number of rear axle idler wheels allowed. Rear axle may be moved upward in the slide rails to accept larger idler wheels.
