By 1973 two-stroke powered motorcycles dominated off-road competition of all types. Yet in 1972, Triumph Corporation, USA decided to field an ISDE team of three riders on their 500cc four-stroke twin, the TR5 Trophy Trail.

The International Six Days Enduro is a traditional event held annually at various points on the globe since 1913. With no cooperation from the Triumph factory in England, project manager Bob Tryon and six techs in their Southern California shop, reworked six freshly uncrated stock machines. With a combination of after-market and custom fabricated parts they built one bike, thoroughly tested and perfected it, went about completing six total and headed for Pittsfield, Massachusetts, the site of the 1973 ISDE. Dave Mungenast, John Greenrose and Ken Harvey each finished this grueling enduro with silver medals, a great accomplishment made greater when considering the technical status of their machines.

Opening his dealership in 1965, the late Dave Mungenast was one of the earliest Honda motorcycle dealers in America. A gentleman and successful entrepreneur, Mungenast went on to become a large and successful multi-brand, multi-location automobile dealer in St Louis, Missouri. Today his wife Barbara and his sons run the businesses and maintain Dave’s shared dream, the Mungenast Classic Automobiles & Motorcycles Museum in St Louis.

Triumph TR5 Specifications:

  • Engine: Overhead Valve Vertical Twin
  • Bore & Stroke: 69mm x 65.5mm
  • Displacement: 490cc’s
  • Compression Ratio: 9:1
  • Carburetor: 28mm Amal Concentric
  • Electrics: 12Volt, Coil, Points, Alternator
  • Starting: Kick Starter
  • Primary: Chain Driven
  • Transmission: 4-Speed
  • Wheels/Tires: 3.00 x 21/ 4.00 x 18
  • Wheelbase: 54.5 Inches
  • Claimed Dry Weight: 350 Pounds

This Triumph TR5 is on Loan to the National Motorcycle Museum from the Mungenast Family, St Louis, Missouri. It’s part of the current DIRT RIDING USA exhibit presented by J&P Cycles which includes almost 50 motocross, trials and enduro motorcycles and memorabilia.

2 replies
  1. Phil
    Phil says:

    Great article. Even then , if it wasn’t for the fortitude of an individual , this would never have happened. Cudos to Dave.

  2. Steve
    Steve says:

    1973 was the first time the International Six Day Trials, renamed the International Six Day Enduro in 1981 by the FIM, was held outside the European continent since its origin in 1913. As the original name implies, this event was designed to test both the riders’ and motorcycles’ abilities, endurance, and versatility. It was very hard to finish, let alone medal in the ISDT.

    For Dave, John and Ken to take home silver medals while campaigning outdated and less reliable machines is truly remarkable. Accomplishing this in the first ever American ISDT makes it even better!


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