Big Cat: Panther Model 100

The Panther Model 100's big sloping cylinder makes it one of the most iconic British motorcycles of all time.

  • 1951 Panther Model 100.
    Photo by Phillip Tooth

1951 Panther Model 100
598cc air-cooled OHV sloper single, 87mm x 100mm bore and stroke, 6.5:1 compression ratio, 23hp @ 5,500rpm
Top speed:
85mph (claimed)
Weight (dry):
386lb (175kg)
Fuel capacity/MPG:
3.5gal (13.2ltr)/54mpg (avg.)
Price then/now:

It might not be one of the fastest classic bikes in the world and it never earned a reputation as a racetrack tool, but that big sloping cylinder makes the Panther Model 100 one of the most iconic British motorcycles of all time.

This is a sloper with a history that stretches way back to 1904, when Joah Carver Phelon and Richard Moore started making the P&M motorcycle, using the engine to replace the frame’s front downtube. That same layout was still the most noticeable thing about the last big Panther when the factory closed for good in 1966.

The Panther name first graced a P&M gas tank in 1923 with the introduction of a sports version of the 555cc sidevalve single. But the 1951 Panther featured here is the 600cc Model 100, a bike that is as much at home hauling a double-adult sidecar as it is being ridden solo.

Riders of fast-revving twins might struggle to understand why anyone would want to own a slogging single, but that’s exactly why people like Andy Tiernan love them. “A big single offers tremendous pulling power and reliability while drinking fuel like a kitten lapping milk from a saucer,” Andy says. “P&M quoted 90mpg for a solo and 60mpg with a sidecar. That’s about as optimistic as today’s car manufacturers’ claims, but I can easily get 65mpg.” That’s on an imperial gallon, which is 1.2 U.S. gallons for a U.S. equivalent of 54mpg.

The secret of that pulling power is a flywheel assembly that weighs nearly 30 pounds. Get them spinning and they will store up enough kinetic energy to make a molehill out of a mountain. Yet while P&M described the Panther as a “Heavyweight,” the 1950 Model 100 must be one of the lightest 600cc motorcycles ever designed to haul a sidecar. In spite of having twin exhausts and passenger footrests made out of thick strips of iron — they look like they were made by a blacksmith — the Panther weighs only 386 pounds dry. Not having a front downtube in the frame must have saved a couple of pounds!

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