One Bad 120

Dean and Sara Larson get ready for the 120 Open class at the USCC Grand Cities 100.

Dean and Sara Larson get ready for the 120 Open class at the USCC Grand Cities 100.

For the past few years Larson Racing’s Sara Larson has piloted one of the baddest 120 mods on the planet. Custom-built by Dean Larson, Jonn Olson and Arne Rantanen, the sled is a jewel that hides many unique build secrets. Since Sara’s moving up to a Sno Pro 500 in the Junior class this year, Dean felt it was time to let people know what’s inside the sled that propelled Sara to a pantload of wins and points championships (including five of seven race wins and a points championship last season) on the USCC cross-country circuit. That’s right, this is no snocross mod, it’s built for terrain. Follow along as sledRacer schools you on what makes up a winning 120 mod.

 

 

 

  

About the only stock piece on the whole sled is the tunnel, and even that has been modified with custom running boards and roll panel. It’s topped with a custom seat built to Sara’s specs.

About the only stock piece on the whole sled is the tunnel, and even that has been modified with custom running boards and roll panel. It’s topped with a custom seat built to Sara’s specs.

The hood is a cut down version of the 600 Sno Pro race sled. It’s held on with the stock rubber staps.

The hood is a cut down version of the 600 Sno Pro race sled. It’s held on with the stock rubber staps.

The belly pan is stock Arctic Cat 12, but the bulkhead is a one-off custom aluminum piece designed by Arne Rantanen. It’s a scaled-down version of a ZR bulkhead. Once he had the design finalized and the parts fabbed Arne TIG welded the whole thing together.

The belly pan is stock Arctic Cat 12, but the bulkhead is a one-off custom aluminum piece designed by Arne Rantanen. It’s a scaled-down version of a ZR bulkhead. Once he had the design finalized and the parts fabbed Arne TIG welded the whole thing together.

The front end has a 32-inch stance and uses stock skis. A-arms are chrome moly and spindles are handbuilt by Rantanen. Tanner shocks are off a quarter midget sprint car and are fully rebuildable and re-valveable. Springs are stock Cat 120 pieces. Rantanen said if he had to do it over again he’d lay the spindles back more because he thinks they sit to upright.

The front end has a 32-inch stance and uses stock skis. A-arms are chrome moly and spindles are handbuilt by Rantanen. Tanner shocks are off a quarter midget sprint car and are fully rebuildable and re-valveable. Springs are stock Cat 120 pieces. Rantanen said if he had to do it over again he’d lay the spindles back more because he thinks they sit to upright.

Drop link steering has no slop and features custom brackets and mount. Notice the brace that spans the bulkhead space between the shocks.

Drop link steering has no slop and features custom brackets and mount. Notice the brace that spans the bulkhead space between the shocks.

That brace is held rigid by a unique set of spars that mount to the steering hoop. Another set of braces carries the load back down to the tunnel. The whole setup is reminiscent of modern sled designs and makes for a very rigid chassis.

That brace is held rigid by a unique set of spars that mount to the steering hoop. Another set of braces carries the load back down to the tunnel. The whole setup is reminiscent of modern sled designs and makes for a very rigid chassis.

The engine is an Arctic Cat 120 modified by Dean Larson and Fred Olson. It is fed by a stock carburetor that’s been bored out and fitted with a custom velocity stack.

The engine is an Arctic Cat 120 modified by Dean Larson and Jonn Olson. It is fed by a stock carburetor that’s been bored out and fitted with a custom velocity stack.

Power is fed through Junior clutches, the same you find on a junior dragster. The sled uses a Dayco belt. The sled features a jackshaft and chain/gear drive.

Power is fed through Junior clutches, the same you find on a junior dragster. The sled uses a Dayco belt. The sled features a jackshaft and chain/gear drive.

A driveshaft-mounted brake is basically the same stuff you’d find on a mountain bike. The mechanical caliper is mounted with custom brackets.

A driveshaft-mounted brake is basically the same stuff you’d find on a mountain bike. The mechanical caliper is mounted with custom brackets.

Custom brake lever is built to Sara’s specs.

Custom brake lever is built to Sara’s specs.

Throttle setup is off an ATV, kill switch is off the race sled.

Throttle setup is off an ATV, kill switch is off the race sled.

The skid is a scaled-down version of a ZR and uses Tanner shocks. Dean spent countless hours working the bugs out of the skid and in its final version worked pretty good. But in the end his only comments on the skid were that if he had to do it again he’d do it different.

The skid is a scaled-down version of a ZR and uses Tanner shocks. Dean spent countless hours working the bugs out of the skid and in its final version worked pretty good. But in the end his only comments on the skid were that if he had to do it again he’d do it different.

Dean’s original version of the scaled-down ZR skid had problems keeping track tension, so he designed a custom version of the Torque Sensing Link, seen here where the rear arm mounts to the tunnel. It worked, kind of. Dean says you’re dealing with such small parts and different degrees of movement on the 120 that things don’t always transfer over from the full-sized sled like they should. Track is stock Cat fitted with ice screws. Drivers are oversized external fitted to a custom hex gun-drilled driveshaft.

Dean’s original version of the scaled-down ZR skid had problems keeping track tension, so he designed a custom version of the Torque Sensing Link, seen here where the rear arm mounts to the tunnel. It worked, kind of. Dean says you’re dealing with such small parts and different degrees of movement on the 120 that things don’t always transfer over from the full-sized sled like they should. Track is stock Cat fitted with ice screws. Drivers are oversized external fitted to a custom hex gun-drilled driveshaft.

Fuel tank is aluminum with a custom-sewn cover. If the guards for the clutches and gears look familiar it’s because they’re clutch guards off an F sled that have been custom fitted to the 120. Handlebars are custom bent chrome moly.

Fuel tank is aluminum with a custom-sewn cover. If the guards for the clutches and gears look familiar it’s because they’re clutch guards off an F sled that have been custom fitted to the 120. Handlebars are custom bent chrome moly.

Custom taillights, an elegantly fabbed bumper and a custom-fitted snow flap really complete the look of the sled.

Custom taillights, an elegantly fabbed bumper and a custom-fitted snow flap really complete the look of the sled.

 

While Sara’s racing career is moving forward in the Junior class next year, Dean says her mod isn’t for sale. He says he’s going to put it on display in the downstairs game room of the Larson home.

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