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The “Plymouth Monster” Motorcycle

Despite the bleak economic condition of the country in the mid thirties, the spirit of adventure was very much alive and well, especially in the world of speed. It was an “Age of Speed,” and the place to be was the Bonneville Salt Flats in Utah.

Plymouth Monster demonstrated

The challengers on “the Salt” were mostly British, using specially built race cars in their quest for the magic title of the “Fastest Man on Earth.” Even today, men still talk about the greats, like Captain George Eyston and Sir Malcolm Campbell. It was even reported that the then-huge sum of $10,000 would be paid to the first man to drive a motorcycle at 300 miles per hour.

Plymouth motorcycle

Fred Luther, a Chrysler employee, prevailed upon the company to supply him with motive power in his challenge to become this man. Chrysler sent Luther a complete 1934 PF six cylinder engine and transmission. Already an experienced motorcycle racer, Luther began the necessary modifications to accommodate its new power plant.

The bike was built around a heavily modified Henderson “X” cycle. First, the frame was lengthened and strengthened; then the engine was mounted lengthwise in the chassis. The steering was mounted far back on the frame, with a heavy roller chain to reach a shaft on the front fork. There were skid plates on either side to keep the bike in upright and to slow it down on the salt. Firestone supplied 8 ply, 30 x 5” treadless tires. A car-type battery was used, along with a huge radiator, vacuum clutch, and tachometer; no aerodynamic concerns appear to have been considered.

Plymouth Monster

The engine was sent to the speed shops of Harry Miller, a name all too familiar to losers at Indy’s famed brickyard. Normally rated at 77 horsepower at 3,600 rpm, the six came out snorting 125 horses at 4,500 rpm. It weighed 1,500 pounds and was nearly 11 feet long. The rider sat just in front of the rear tire and lay flat over the frame.

The bike was built over the winter of 1934-35 and made its appearance on the Bonneville Salt Flats in 1935. There, under the watchful eye of the official timers, Fred Luther set out on his way to fame, glory and hopefully, $10,000 in prize money.

The rules at Bonneville were the same then as they are today. To qualify for a record you must run the course both directions, down the course and then back again, with the average speed used to nullify wind effects.

Luther pushed the bike on the first leg of the record attempt and got the bike up to a speed of 140 miles per hour. On the return run, feeling more confident, Luther continued to "open up" the engine until trouble struck—he broke a connecting rod at about 180 miles per hour— and the bike was still in second gear!

Luther decided he had enough of the record attempt and never again attempted to reach the 300 mile per hour mark. He felt that the Plymouth Henderson X-Miller combination could reach that lofty figure, if anyone would ride it that fast. There were no takers lurking in the shadows, however. 300 miles an hour on a motorcycle in 1935 was indeed a lofty goal.

Plymouth motorcycle

At around the same time as Luther’s attempt at the Flats, Sir Malcolm Campbell climbed into his Bluebird race car and became the first man in the world to drive an automobile at a record speed of 301 miles per hour.

As to the $10,000 prize for breaking 300 mph in a motorcycle—too late, the money turned out to be a hoax. There was no sponsor waiting to bestow that astronomical sum upon some brave and daring motorcyclist.

Fred Luther returned home with his broken cycle, out about $3,000, and probably with a few more gray hairs than he started his ride with—but the motorcycle powered by a Plymouth Six was quite an adventure. One can’t help but wish that he had set that record.

What happened to the Plymouth Monster

Louie Fisher and Gideon Giroux bought the “Plymouth Monster” from the Hensley Estate in 1992; Dean Hensley had the foresight to collect old racing bikes when few people paid any attention to them. He also saved the Bert Munro special (the world’s fastest Indian).


Louie and Gideon researched every piece of the bike to make sure it was original, like the vacuum operated clutch and the evolving final drive they used after the Henderson drive system failure at the Muroc dry lake test in California. I restored it to be as it ran in 1935 at Bonneville.

Gideon wrote, “Lou and I absolutely love this bike and the pioneer spirit of the people that built and raced them. We are proud to be able to be the caretakers of such a wonderful piece of American racing history.”

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