2019 Pro Stock Snowmobile Rules
PRO STOCK SNOWMOBILE
PRO, preceded by the sled number
Reserved for 2000 or later year stock-appearing, gasoline burning, snowmobiles built for drag racing competition.
All snowmobiles must be configured as a stock qualified production snowmobile and retain OEM stock appearing profile. Any motor/chassis may be interchanged within brands. All components that are allowable for modification must retain structural and mechanical integrity.
REQUIREMENTS & SPECIFICATIONS
2 STROKE 3 CYLINDER CARBURETED ENGINE COMBINATION
Any OEM snowmobile crankcase within brand is permitted. Must be a two (2)-stroke, 2 cycle naturally aspirated, case reed engine with a limit of 1000cc (+2%) displacement and is limited to three (3) in line cylinders. Any commercially available aftermarket cylinder and cylinder head is allowed. Any bore/stroke is permitted. Billet crankcases and engine components are allowed. All crankcases must maintain stock bore centers and be sized to accept stock crankshaft components for the brand. Stock crankcases may be modified to change or relocate reeds. All reeds must be commercially available. Nitrous oxide, super charging, turbo charging is NOT permitted. A maximum of one (1) venturi per cylinder will be allowed. Any commercially available aftermarket carburetor is permitted. Fuel pump may be modified and/or changed from original. If an electric pump is used, it must have its own separate shutoff. Air boxes are optional. Minimum weight is 650 pounds with rider and gear.
2 STROKE 3 CYLINDER EFI ENGINE COMBINATION
Rules are essentially the same as for the Carbureted combination with the following exceptions; any throttle bodies, any injectors, FuelTech or Electromotive ECU. Also review Ignition section. Minimum weight is 650 pounds with rider and gear.
2 STROKE 4 CYLINDER CARBURETED YAMAHA COMBINATION
Any OEM snowmobile crankcase within brand is permitted using stock bore centers. Must be a two (2)-stroke, 2 cycle naturally aspirated, cylinder reed engine with a limit of 1000cc (+2%) displacement and is limited to four (4) in line cylinders. Any commercially available aftermarket cylinder and cylinder head is allowed. Any bore/stroke is permitted. Billet crankcases and engine components are allowed. All crankcases must maintain stock bore centers and be sized to accept stock crankshaft components for the brand. Stock crankcases may be modified to change or relocate reeds. All reeds must be commercially available. Nitrous oxide, super charging, turbo charging or fuel injection is NOT permitted. A maximum of one (1) venturi per cylinder will be allowed. Any commercially available aftermarket carburetor is permitted. Fuel pump may be modified and/or changed from original. If an electric pump is used, it must have its own separate shutoff. Air boxes are optional. Minimum weight is 675 with rider and gear.
4 STROKE TURBO COMBINATION
Limited to twin or triple cylinder applications available on production sleds. Must use Stock OEM (unaltered) turbo correct for the application, OEM air to air intercooler and associated components, stock, Vi-Pec or Link ECU. Also review Ignition section. Displacement must be no less than OEM or no more than 1122ccs . Nitrous oxide or super charging NOT permitted on four-stroke engine. Any commercially available aftermarket cylinder and cast cylinder head is allowed. All crankcases must maintain stock bore centers and be sized to accept stock crankshaft components for the brand. Minimum weight is 735 pounds with rider and gear.
Any functionally silenced exhaust modification or replacement is allowed. (Silencers are optional) Exhaust must exit from the side of the machine and may not protrude more than 3 inches beyond chassis or hood.
Exhaust valves optional. Exhaust valves shall be guillotine-type slide valve only. Valve control is limited to exhaust gas pressure sensing bellows-style diaphragms acting against return springs. Exhaust gases must act directly on the diaphragms. Servo operated valves are not allowed.
For the 2 Stroke applications: NHRA-specified Sunoco SR-18 or Sunoco Maximal or VP equivalent racing gasoline mixed @ a 32:1 (baseline) ratio with either Legend 2X-2SR Racing Oil or Lucas Oilís Two-Stroke Racing Oil. Dielectric Constant, as per NHRA DC meter, must match baseline reading of specified gasoline/oil mixture. The use of other additives is prohibited.
For the 4 Stroke applications: NHRA-specified Sunoco SR-18 or Sunoco Maximal or VP equivalent. See General Regulations 1:6.
Artificial cooling or heating systems (i.e. cool cans, ice, Freon, etc.) prohibited. Circulating systems not part of normal fuel pump system prohibited. Electronics, pneumatics, hydraulics, or other devices may in not way affect the fuel system, including the venting system. All Pro Stock Snowmobiles must be equipped with a positive-lock drain valve located between the fuel tank and the carburetors to facilitate removal of fuel samples for fuel-check purposes.
Any commercially available snowmobile clutch and drive belt are allowed. Chains, pulleys, belts, and exposed moving parts must be isolated from the driver and other competitors by securely mounted shield(s) capable of retaining all accidental explosions and component impacts. No holes may be drilled in protective shields. Drive belts must be commercially available and manufactured in sufficient quantity for over the counter sales. Clutch covers are mandatory. Clutches must be covered down to the center of the clutch bolts. Clutch cover is constructed of minimum 0.125 inch 6061-T6 or 7075-T6 aluminum.
Camoplast Challenger 9897R, 9895R or 9896R asphalt tracks are the only tracks permitted for competition. No modification allowed. Any track at or below wear bar marks will not be permitted. Tracks must be installed with direction arrows correct. No traction type compounds may be applied to tracks. Artificial heating of track is prohibited.
SKIS AND WHEELS
Skis shall be constructed in accordance with illustrations provided in Section 4E- E.T. Snowmobile. The minimum length is fifteen (15) inches and the maximum length is twenty-one (21) inches. Both skis must be identical and not staggered on the snowmobile. Ski distance (center to center of the wheels) is to be a minimum of forty (40) inches and a maximum of forty-five (45) inches. The area under the snowmobile, measured from the rear of the skis to point where the measuring tool comes into contact with the front of the track, must be a minimum of two (2) inches. Ski loops must be 1inch O.D. either aluminum or steel tube, but may be taped or fitted with plate. All steering wheels shall be of materials specifically designed for snowmobile use on a dry surface.
BRAKES AND SUSPENSION: 3
Lower drive shaft brake is required. Brake system shall be hydraulic hand lever operated disc brake with a disc diameter minimum of seven (7) inches with a minimum thickness of 3/16-inch. Braided steel brake lines mandatory. Brake lines to be mounted and routed to ensure no contact with moving parts. Integral chain case to bulkhead allowed providing brake assembly is relocated to the drive shaft. Drive shaft brake system located outside the tunnel must be enclosed.
Handlebars, handlebar grips and controls may be modified. Brake and throttle controls must maintain stock configuration. No twist type throttles or rotating throttle from stock position allowed. Welded aluminum handlebars prohibited.
Currently accepted cable steering is allowed. Minimum cable housing diameter is 0.500 inch.
Any aftermarket or OEM track suspension is permitted. Modifications to OEM or any commercially available aftermarket suspensions must maintain structural integrity.
Front suspension and shocks must be in a position that maintains stock appearance and is representative of the year, make and model of the snowmobile. Interchanging of ďTrailing ArmĒ and ďA-ArmĒ suspensions within brands or models is prohibited. Stock spindles may be strengthened or replaced with a stronger spindle. For replacements, minimum wall thickness is 0.120 inch and the minimum outside diameter is 0.750 inch. An inspection hole is required if the wall thickness is not visible. If modifications to suspension parts are made, structural integrity must be maintained.
For non Turbo applications:
Snowmobile must resemble stock model of particular brand. Seat, windshield and tunnel must be stock appearing. Windshields are required. Commercially available aftermarket and custom frames permitted. Design and integrity are subject to tech inspection. ALL aftermarket and custom frame components except braces, brackets, and gussets must be manufactured from 4130 chromoly tubing and plate or 6061-T6 aluminum plate. Use of stock OEM bulkhead allowed and reinforcement allowed. All welding must be done by approved TIG heliarc process. Grinding of welds is prohibited. All components must maintain structural integrity. Stock tunnels may be used with any commercially available aftermarket or custom front end. Motor mounts and jackshaft may be changed from original location. Any engine location is allowed as long as stock snowmobile profile is not compromised. Overall length is limited to 96 inches as measured from center of ski mounting bolt to center of rear axle. Minimum height (as measured at the steering crown) will be 30 inches, unless OEM height is less.
For Turbo applications:
Must be stock chassis as purchased from sled manufacturer/dealer using applicable conversion for asphalt skis, track, etc.
Chain case is required. Chain case can be stock or commercially available aftermarket enclosure. Any chain case modification allowed.
Ballast permitted, must be securely bolted to the frame by a minimum of one 3/8-inch bolt per five (5) pounds.
For Stock or aftermarket stock appearing tunnels allowed for non Turbo applications. Tunnel material minimum 0.050-inch 6061T6 aluminum if used. Tunnel may be reinforced with similar aluminum plate or chromoly tubing. The tunnel may not extend more than twelve (12) inches beyond rear axle center.
For Turbo applications: Must be stock chassis as purchased from sled manufacturer/dealer.
A stock fuel tank may be modified to accommodate a fuel cell or smaller tank. The OEM style outside shell must remain intact. A fuel cell cap may replace the original fuel cap. Fuel systems must be equipped with an accessible outside shut-off valve.
Running board footstops are permitted, but may not be wider than the running board at the position they are installed. They may not extend higher than the top of the tunnel at the point of installation. If used, footstops may not be mounted more than 54 inches as measured in a straight line from the center of the handlebars to where the footstop attaches to the running board.
Front air dams are permitted. If air dam is mounted perpendicular to the skis, it must maintain a minimum of one-inch (1") ground clearance. If air dam is mounted in front of or behind the skis, it must maintain a minimum of two inches (2") ground clearance from ski to ski. The area under the snowmobile, measured from behind one ski to the other ski, must be a minimum of two (2) inches above the ground and a minimum of two (2) inches wide behind the ski. Air dam is not permitted to extend past the front OEM bumper or three (3) inches past belly pan, whichever distance is greater.
No additional bodywork that changes stock appearance allowed. Ventilation openings may be covered. Suspension side skirts are prohibited. Aerodynamic devices, airfoils, wings prohibited. Openings for component accessibility will be allowed. The hood and belly pan may be removable as long as the OEM appearance for the said model is maintained and structural integrity is intact. After market body panels and approved duplications of production bodies of fiberglass or carbon fiber are permitted.
Stock or custom seat made of steel, aluminum, fiberglass or carbon fiber permitted. Magnesium prohibited. Stock seats may be cut down for lower profile. Seat must maintain stock configuration. Riders must sit in upright position. Seat, foot stops and handlebars shall be positioned such that the angle encompassed between the riderís knee, waist and torso does not exceed ninety (90) degrees. In other words, the riderís knees may not be further back that the riderís hip/pelvis.
IGNITION (All Applications)
Any snowmobile OEM ignition, and MSD # 00-00-2530 (designed for snowmobiles), MSD 7530T, 75301, 7530, and Power Grid, Electromotive TEC GT, TEC 3R, FuelTech FT500, FT500 Lite and FT600 ignitions are allowed. No additional electronics/devices to aid in down-track RPM limiting will be permitted. Traction control is prohibited. (See Section 20- General Regulations Paragraph 9:11 Traction Control).
Snowmobile must be equipped with a positive ignition-cutoff switch attached to the rider with a lanyard. Snowmobile must also have a handlebar mounted ignition-cutoff switch.
A functional taillight is mandatory for night operations. Flashing/strobe lights prohibited.
SUPPORT GROUP: 9
Permitted for information gathering only. Throttle operation, clutch engagement, etc. are to be solely under the control of the rider. Traction control devices not permitted. (See General Regulation Section 20)
WARM UP STANDS
Must be used when warming up the engine. Lanyard cord (tether cord) must be attached to someone anytime engine is running. Starting/Running of sleds in the pits for the purpose of tuning, warm up, etc. is limited to a period of 1 hour before a scheduled run.
Some form of substantial noise reduction equipment required when snowmobile is running in the pits. Failure to utilize noise reduction equipment may result in Event Disqualification.
A valid NHRA competition License is mandatory.
Full-faced helmet meeting Snell M2010, K2005, K2010, SA2005, SA2010, SA2015. Shield mandatory. See General Regulations 10:7.
Full all-leathers or SFI Spec 40.1/2 suit mandatory. Two-piece suits must be joined at the waist with a metal 360-degree zipper. Jacket and pants or suit meeting SFI Spec 40.1/1 or 40.1/2 (or leather jacket), leather boots/shoes above the ankle, and leather gloves mandatory. Gloves must be Kevlar-lined or equipped with slide buttons. See General Regulations 10:10.
All general safety requirements apply as specified in current year NHRA rulebook. In the case of other class specific rules questions, the NHRA rulebook and/or NHRA rules Revisions will be consulted.