CLASSIC MOTOCROSS IRON: 1975 ROKON RT340MX AUTOMATIC

On Mar 30, 2023 Last updated Mar 29, 2023

Rokon is still in business today selling its iconic two-wheel-drive Trail Breaker model at www.rokon.com.

By Tom White

Racers have always dreamed for decades about automatic transmission motocross bikes. Today, we are closer to that reality than ever with point-and-shoot electric-powered bikes, but, back in the day, the automatic dream was hard to fulfill. The most famous automatic motocross bike was the Rokon RT340MX (only produced in 1975-’76). It was powered by a 335cc, Sachs, two-stroke snowmobile engine. The Rokon utilized a Salisbury torque converter for a truly automatic transmission. The torque converter allowed the engine to run between 6000 and 6700 rpm most of the time. The most famous Rokon motocross racer was Florida’s “Rokon Don” Kudalski. He won several races for the Rhode Island company, including the Open class at the 1976 St. Petersburg, Florida Inter-AMA. Bob Harris, Ron Bishop, Dave Mungenast and Jim Hollander were also major players in Rokon’s short history in off-road racing.

The 335cc Rotax snowmobile engine was fired up with a pull rope. It wasn’t as easy as it sounds. Note the rear facing rear brake pedal and KH rear brake master cylinder.

Riding a Rokon 340MX was unique, since the torque converter didn’t provide any engine braking. Rokon’s cure was to mount touchy KH disc brakes (eight years before any of the other manufacturer). Although you didn’t have to shift the 340MX, you had to deal with the bulging belt and pulley gears that made the Rokon incredibly wide. The transmission belt was vented to the outside for cooling, so it was easily contaminated by water that could cause slipping. Riding on loose surfaces was sometimes complicated, as “tire spin” didn’t cause a change in engine sound. Plus, since it was a snowmobile engine, you started it with a lawnmower-style pull rope.

The front and rear brakes used solid undrilled rotors. There was no shift lever or clutch lever.

MXA’s Jody Weisel raced a 1976 Rokon 340MX Cobra. He says, “You didn’t have to shift, just wick it up and hang on. It made strange noises as the belt slid up and down the cone-shaped pulley gears. It was fast and even faster when you chopped the throttle because it freewheeled. The first time I grabbed the solid rotor disc brakes at the end of a fast straight, I was catapulted like a Guernsey cow from a French trebuchet. I landed with 275 pounds of Rhode Island-built snow blower on top of me.”

In the end, the development costs of the 340MX bikes drove Rokon into financial difficulty. Only 335 machines were ever produced, and production of the 340MX ended in 1976. Today, Rokon is still building its classic two-wheel-drive Trail-Breaker in its Rochester, New Hampshire, factory.

Suggested retail in 1975 was $1450. In 1975 and 1976, Rokon offered the RT340MX motocrosser, FT340 flat tracker and ST340 street model. The “Cobra” was the hopped-up version. The bike has never been popular with vintage motorcycle collectors, but if your want to buy a collection worthy Rokon 340MX, make sure it has a good rope pull-starter, Betor forks, Red Wing shocks, Preston Petty fenders and KH disc brakes. The stock pipe, muffler (with two snorkels) and a set of magnesium snowflake mag wheels are bonuses.