USSA Class Description for the 2012 to 2013 season.

Junior stock: This class is for Junior competitors aged from 10-13 years of age competing on ISR specified sleds. Legal sleds for this class are as follows: Arctic Cat; Puma/Jag 340 and Z 370, Polaris; Indy Lite 340, Indy 340, Indy 340 Deluxe and 340 Edge, Si-Doo; Formula S368, MXZ 380, Freestyle 300, and Tundra 300, Yamaha; Ovation 340. This is a beginner class on limited horsepower sleds with little or no changes allowed from stock production. This class has a speed limit that may be enforced if track size dictates it for safety purposes. Rules are found in the ISR rulebook for 2012 on pages 135-136.

Junior I Sprint: This is a modified class for Junior competitors aged 12-15. It utilizes an open chassis purpose built sled and a stock air cooled engine of a 380 cc maximum. Engines must come from the following production brands, Arctic Cat 370, Ski Doo 380, Polaris 340, and Yamaha 340. Engine must be used in stock trim; the factory “wye” pipe must be used. The air box may be removed and the exhaust system after the “wye” pipe may be modified. Rules for this class are found on pages 131 and 132 of the 2011 ISR rulebook.

Junior II Sprint: This is a modified class for Junior Competitors aged 14-17. It utilizes an open chassis purpose built sled and a stock air cooled engine of a 600 cc maximum.  Engines must be stock qualified 600 cc or less displacement engines from current production sleds. Rules for this class are found on page 132-133 of the 2011 ISR rulebook.

Junior I F-500: This class is for competitors aged 11-13 utilizing a legal F-500 sled. The sled must be restricted in the following manner to be able to compete. The gear ratio is fixed at 15/39 and a carburetor restrictor plate must be used between the carburetor mounting boot and the cylinder.  Restrictor plates are available from the USSA Director of Competition and have a deposit required. This class allows a family with an F-500 sled the ability to run the unit in both adult and junior classes. Rules for this class are found on the USSA website.

Junior II F-500: This class is for competitors aged 14-15 utilizing a legal F-500 sled. The sled will compete in legal trim for the adult F-500 class. This class allows a family with an F-500 sled the ability to run the unit in both adult and junior classes. Rules for this class are found on the USSA website.

F-500: This class is an entry level budget class, utilizing 1989 to 1992 Polaris Indy 500 Chassis and engines. The class offers close competition for many riders at an affordable price. Chassis are allowed limited modifications to improve handling, and hoods, seats, dashboards, and other cosmetic items are allowed to be changed or modified to enhance creativity and uniqueness.  Rules for this class are found on page 74 of the ISR rulebook for 2012. Please review as several new rules and limitations apply.

Women’s F-500:  This class is available to Women age 16 and up. It follows all the same operational and technical rules as F-500.

F-500 Sport: This class is an entry level budget class, utilizing 1989 to 1992 Polaris Indy 500 Chassis and engines. The class offers close competition for many riders at an affordable price. Chassis are allowed limited modifications to improve handling, and hoods, seats, dashboards, and other cosmetic items are allowed to be changed or modified to enhance creativity and uniqueness.  Rules for this class are found on page 74 of the ISR rulebook for 2012. Reduced entry fee, non point class, winner receives a commemorative checkered flag. Top points riders from previous season may not enter.

Sportsman 600: This is a regional class offered by USSA utilizing 1983 to 2000 production chassis and engines. This class is limited to 600 cc liquid cooled engines maximum displacement. It is designed as a budget, introductory class and is titled “Sportsman” to indicate that while it observes many stock restrictions, it does allow some builder creativity. The class is stepping stone class to full mod chassis classes, and offers fast racing, good handling, and excitement. Rules for this class are found on the USSA web site.

Combo:   This class is provided as an entertainment class for riders of the F-500 division and the Sportsman division.   Sleds must remain legal for their base class when they compete in this class. The class pits the smaller displacement, but lighter, F-500 sleds against the Sportsman 600 powerhouses. In addition to the opportunity to run a second class for these budget sleds, track size, configuration, and driver ability allow the class to offer unbelievable racing excitement. Refer to the USSA web site for individual class rules.

LTD 500: This class started as a regional class in USSA, but now is an accepted ISR class for stock engine participation. This class requires a maximum displacement stock 500 cc liquid cooled engines and “wye” pipe but allows exhaust modifications and an open, purpose built chassis. The class was created to offer a reprieve from the existing stock classes offered prior to 2010 that required stock engines and stock chassis, but allowed for extremely expensive chassis modifications that were not productive to garnering large groups of riders due to the expenses involved.  The class allows 2009 and previous stock class sleds a place to race, along with the purpose built Limited class sleds.  This class is quite successful and is the base for the Ltd 600 class. Rules can be found in the 2012 ISR book on page 75.

LTD 600: This class started as a regional class in USSA, but now is an accepted ISR class for stock engine participation. This class requires a maximum displacement stock 600 cc liquid cooled engine and “wye” pipe but allows exhaust modifications and an open, purpose built chassis. The class was created to offer a reprieve from the existing stock classes offered prior to 2010 that required stock engines, stock chassis, but allowed for extremely expensive chassis modifications that were not productive to garnering large groups of riders due to the expenses involved.  The class allows 2009 and previous stock class sleds a place to race, along with the purpose built Limited class sleds.  This success of the LTD 500 class is the base for the Ltd 600 class. Rules can be found in the 2012 ISR book on pages 75 and 76.

Pro Sprint 600: This modified class uses air cooled engines of 600 cc maximum displacement and limited carburetion. This class is extremely fast for the engine package and offers an open field for chassis and engine builder creativity. This class has the same speed potential on smaller tracks as Champ 440 sleds and sometimes “promoter option” classes are created to allow the two classes to compete. The builders in this class are highly talented in both suspension geometry and engine development. Rules for this class are found on page 72 of the ISR rulebook for 2012.

Pure Stock 600: This class that requires a 600 cc maximum stock production  2007 or newer sled be used in stock trim. Modifications are extremely limited, and are limited to minor suspension tie down, clutch and carb tuning, and specified carbide limits. This class is designed to return stock class racing to a “stock” category and not the highly modified units that competed as “stock” sleds in the past. This is the inaugural year for the class. It is ISR approved and rules are found on pages 68 and 69 of the 2012 ISR book.  

Champ 440: Champ 440 is the Premier USSA class; it utilizes 440 cc maximum liquid cooled engines with restricted carburetors and an open exhaust. Chassis limitations are primarily weight and width. This high powered open design class is the base for the Worlds Championship class and is recognized throughout the snowmobile race world as the “professional” class of competition. Rules for this class are available in the ISR rulebook for 2012 on pages 71 and 72.

OUTLAW:  Outlaw 600 is a stock based engine class with a spec concept chassis. Outlaw 600 competitors must be aware that the first year is a test bed and proving grounds. Rules can and may be changed during the season o improve safety or equalize performance.The class is an enclosed cockpit class, with a 600 cc power plant and a rear mounted third ski that supports the driver weight inside the roll cage. Designed to perform similar to sprint cars, the sleds exhibit more of a sliding style, carry strong top speeds, and feature a rolling start race event. Comprehensive rules are found on pages 69-71 of the 2012 ISR rulebook.

Vintage Pro Mod Classes

Pro Mod 300- Pro Mod 340- ProMod 440- Pro Mod 650- Pro Mod 800

These classes are offered by USSA to feature a variety of competitive Vintage racing for the fans enjoyment. All classes are under the rules indicated for the class in the current ISR book.

Class Structure