1. Pro Imp snowmobiles must retain OEM stock appearance for the
model (hood, seat, engine and tunnel must retain OEM appearance and
dimensions.) Like chassis may be interchanged with in the brand.
2. Machine movement will be from Stock to Pro Stock. Any snowmobile
may be reclassified and assigned in the interest of fair competition.
3. Sled must begin as a qualified stock snowmobile. All sleds must
comply with the GENERAL RULES AND REGULATIONS section.
4. Any alterations allowed in Stock classes are also allowed.
5.Class Jumping is allowed within this class and to the Open
6. stock gauges only
7. Tech Vest is MANDATORY
1. The engine may be moved from its OEM location and remounted a
maximum of one (1) inch in any direction, which is perpendicular to
the centerline of the crankshaft. The crankshaft may not be moved
within the crankcase.
2. Crankcase, cylinders and crankshaft must be from the same model.
These components may be modified internally provided the engine
retains its complete external stock appearance and dimensions. Must
retain original number of cylinders.
a. Four cylinder crankshaft gears may be changed with any OEM
b. Cylinder maximum overbore is defined as 2% over the cc
displacement for the class.
c. Cylinder may be bored or sleeved down.
d. OEM cylinder outer shell dimensions modification must be
within .020 inches per side / .040 overall of the OEM cylinder.
Modification must be blended into original casting to retain
e. Cylinder height may be modified to change port height. If a
plate is used to raise cylinder height, the plate, including
gaskets, cannot exceed ½ inch.
3. Engine components allowable for modifications or replacement:
d. Pistons, pins and rings.
f. Manifolds (intake)
g. Carburetors (no super charging, turbo charging or aftermarket
must remain OEM for the model. A maximum of one venture
per cylinder will be allowed.
h. Diad carburetors are allowed as per ISR.
i. Air boxes may be removed.
j. Motor mounts
k. Reeds and reed blocks may be changed if the do not change
the outside dimensions of the cylinder or crankcase. External
plate may be thicker. Pro Stock 1000 reed cages may be
modified. No welding allowed. Reed cage changes must
accomplished by bolting only.
l. Fuel pump
4. Dual spark plugs allowed as long as stock appearance is not
5. Engine must retain original cooling concept. Cooling circuits may be
modified or removed.
6. Water pumps may be removed.
7. Radiators and ducting may be used but may not change OEM
8. Any exhaust modification or replacement is allowed, with the
exception on megaphones. The exhaust system emission pipe must not
protrude more than three (3) inches beyond the chassis or hood
1. Any CVT clutches allowed.
2. Clutch jackshaft may be changed or modified (no welding on jackshaft)
3. The jackshaft and track drive axle may be moved from their OEM
locations a maximum of one inch in any direction which is
perpendicular to the centerline of the shaft.
4.Stock chain case only
5. Minimum brake disk diameter is 7 inches (if disk is mounted to track
drive axle and a dual opposing piston caliper is used, the disk minimum
diameter is 6 inches.)
6. Brake caliper may be either dual opposing piston or single piston type.
SKI SUSPENSION & STEERING
1. Material substitution is allowed. OEM appearance must be maintained.
2. Front suspension components including struts, arms, spindles, rod ends,
spherical joints, tie rods, linkages, IFS trailing arms and radius rods
must remain OEM design. Must remain in the OEM location on the
3. Any shock absorber allowed. Must remain OEM location on the
4. Spindles may be strengthened or replaced with a stronger spindle.
Spindle height must remain within 10% of the original OEM
5. Minimum ski stance (center to center of the ski runners) is 40 inches.
6. Ski widening devices allowed. Maximum overall width is 45 inches.
7. Handle bars, grips and controls may be modified.
SKIS & SKI RUNNERS
1. Any OEM or aftermarket ski may be used provided the original spring
concept remains the same. Minimum length is 20 inches.
2. It is highly recommended, if a cutting edge is used on a ski, that no
more than 5 inches 90% cutting edge be used on a ski.
3. Ski loop must be designed to prohibit ski interlock with any other
component while driver is on the machine.
1. Stock rails only is allowed.
2. Stock suspension only.
3. Dual limiter straps required. One inch of travel required with driver
sitting on the machine.
TRACK & TRACTION
1. Speed Track with picks only
2. Speed Track must not be trimmed or narrowed
3.Except for under slide rails, all plates will be no greater than 3.25
inches in width and length. Kicker plate must be located under slide rail
and be no longer than 11 inches and no wider than 1.25 inches
4.No Steel Cleats allowed.
5. Only picks allowed with no chisel studs must be pointed studs
FRAME & BODY
1. Chassis including front bulkhead must retain OEM appearance and
dimensions for the model. Material substitution is allowed. Steel may
be substituted with aluminum. Tubular front end are not allowed. The
race director shall have the authority to determine structural integrity.
2. Openings must be closed, Cowling, etc. may not be cut or shaved down
(OEM appearance must be maintained.)
3. Access opening s for component accessibility will be allowed, but must
be closed with original type materials.
4. Chassis reinforcement will be allowed. No lightening holes can be
drilled that alter the outside appearance for the model. Structural
integrity must be maintained.
5. Hood to belly pan molding must remain intact. The molding may be
lightened as long as it does not alter the outside OEM appearance.
6. Any insulation can be removed.
7. Seat must remain stock appearing. Seat may be lowered but must be at
least two inches thick at its minimum dimension.
8. The fuel tank may be modified to accommodate a fuel cell. The outside
gas tank shell must remain intact. The fuel cap may be replaced with
the fuel cell cap. The use of a fuel cell is used with the above rule will
not compromise OEM appearance.
9. Except for front air dam (which requires 2inches clearance.), all other
parts and components must maintain a minimum of 1 inch ground
clearance with the suspension fully compressed.
10. No Carpet tracks
IGNITION & ELECTRICAL
1. Stock ignition only