MONGREL DOGS, AS IS WELL KNOWN, MIGHT not be as pretty as pedigree pooches, but they do tend to be less highly strung, more dependable, and much smarter. The Trophy Trail/Adventurer is factory mongrel – an actual Meriden-made TriBSA.
Born of troubled times, the TR5T was based around the P51 frame, which was designed for a BSA unit single, the B50 Gold Star/ Victor. With one of the best Triumph twin engines fitted in, it is a model that lasted for only a year and a half but is now one of the most sought-after late Triumphs.
The heart of the matter is Triumph’s proven and capable T100 motor. At the peak of its development, the compact 500cc twin was one of the best British engines ever mass-produced. The T100 knocks out an alleged 38bhp with 9.0:1 compression. It is relatively smooth except at high revs and is fairly easy to start. It is everything, in fact, that the B50 wasn’t. Although the engine was small, it still sits very high in the frame. There were clear gaps between the bottom of the crankcase and the lower frame rails, and this is combined with a lofty-for-the-time 32in seat height.
The engine had some modifications to the cylinder head because it didn’t quite fit well enough in the frame loop for the original top end to be removed with the engine still in the frame. In the days when removing the cylinder head was a common part of British twin ownership, this was a major flaw. Triumph engineers needed to modify the rocker boxes and the middle head studs so this could be easily achieved.
The frame is all-welded, which was something of a departure from the Triumph practice of brazing and bolting frames together that had existed before 1970. There is a four-pint oil reservoir in the top tube,
