A Triton Cafe Racer is one of those motorcycles that every man should own at least once in their lives. The bike is the famous combination of the Norton Featherbed frame and the Triumph parallel-twin engine, often with a slew of other aftermarket parts all designed to make it go as fast as an air-cooled, vintage British twin can possibly manage.
This particular Triton Cafe Racer was built by Christopher Bernardi in New England, he went all out on the build – going so far as to replace every single bearing or bushing regardless of age, he even added a Joe Hunt Magneto to eliminate the sometimes troublesome Triumph unit. It’s running a 1956 Norton Wideline Featherbed frame fitted with a 1960 Triumph Bonneville pre-unit motor that’s been bored out to 750cc (from 650cc), the new Replica Seeley swingarm is wider and better built than the original Norton swingarm (it’s also mounted with bearings instead of bushings).
The front end of the bike may look familiar to you, that’s because it’s off a Suzuki GT750 4LS, the neck stem had to be custom machined to fit Norton-size Timken bearings and the finished look is flawless. The fairing is a Kirby one piece fiberglass race unit and the fuel tank is a polished aluminium Lyta model that’s been internally braced and baffled.
Triton motorcycles were not factory models but were hybrid bikes built in the 1960s and 1970s. Many were privately constructed but some London dealers offered complete bikes. The builders fitted Triumph engines into Norton frames, and the aim was to combine the best elements of each marque and thus gain a bike superior to either. Many Tritons were configured as café racers with single-seats. The name ‘Triton’ is a contraction of Triumph and Norton; and ‘Triton’ happens to be a mythological Greek God.
The Norton Featherbed frame was regarded as the best handling item of the day, and the plan was to replace the standard Norton engine with Triumph parallel-twin engine. A popular engine choice was the Triumph Bonneville unit with twin carburettors and twin camshafts. This pushrod engine gave good performance and reliability and could be more easily tuned for greater power using high-profile camshafts, high compression pistons and twin carburettors. In due course, a Weslake 8-valve head became available for the Triumph motor.
The Norton 650 and 750 vertical twin engines had a reliability problem. At about 7000 rpm the piston exceeds the engineering limit for piston speed, so over-revving soon destroys the engines. The BSA 650 had a bronze bush main bearing on the right hand side, doubling as the crank oil feed, with a lack of effective crankshaft end play control, that all had difficulty staying together when ridden hard, even though the rest of the design was possibly more robust than the Triumph. The Triumph vertical twin used a ball on the timing side, and a roller on the other, with the oil feeding through a separate bronze bush in the outer right hand engine side cover.
Whereas the Norton 650SS 646.44 cc had a bore and stroke of 68 x 89 mm giving 49 bhp (37 kW) @ 6,800 rpm, the Triumph T120 Bonneville 649.31 cc had a bore and stroke of 71 x 82 mm giving 46 bhp (34 kW) @ 6,500 rpm. However the mean piston speed of the Norton was 3,971 ft/min (almost at the, then accepted, limit of 4,000 ft/min). The Triumph, with its shorter stroke, had a mean piston speed of only 3,497 ft/min, had much less vibration and was much stronger and reliable. Road tests showed that the Norton had a higher top speed due to its 3 bhp (2.2 kW) advantage.
In spite of this, the Triumph was the much preferred engine. The Norton featherbed was the preferred frame, hence the Triton.Tritons with a pre-unit Triumph motor sometimes retained the post-1960 Norton AMC gearbox, which was thought superior to the equivalent Triumph gearbox. A Quaife five speed gearbox was sometimes used. More modern Tritons use a Triumph unit construction twin in a Featherbed frame.
Several motorcycle dealers made equipment for Triton conversions, some would do the complete job for customers while others sold complete Tritons. The most important part required are the engine mounting plates and several different designs exist that can affect the engine placement and therefore the handling. The lower the engine is mounted the better the handling achieved from the Norton frame.