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

crankshaft gear.

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

OEM appearance.

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:

   a. Heads

        b. Bearings

 c. Rods

                                  d. Pistons, pins and rings.

       e. Gaskets

                          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.




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.




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.




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




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




1. Stock ignition only