Home-Made Twin-Engine Triumph Motorcycle

When people ask him ‘why?’, he simply replies, “Because, why not?”

AFTER SEEING Trevor’s twin-engine Triumph at a swap meet I just had to track him down and find out more. What makes this one of my favourite bikes and build is Trevor is in his 70s and most of it was done by him.

Over a cuppa he told me this was his third attempt at building his toy.

After starting with twin 350 cc Triumph engines he found the frame had a twist; second attempt he upgraded to twin 500 cc engines and a Triumph rigid rear-end but used the wrong metal piping. Not to worry, he says, and started his third and final attempt with outstanding results. He again upgraded the engines, this time opting for twin 650 cc triumphs.

Both engines were fully rebuilt. He reground the crankshafts and fitted connecting MRP rods, Triumph 3134 camshafts and followers, new pistons, valves and valve springs, and mushroom rocker adjusters. One of the heads needed valve seats. He fitted new Morgo plunger oil pumps, new roller and ball bearings races. He built the engines with negative balance on the cranks. He added belt drive sprockets for the engine coupling, mounted these on Triumph chain drive sprockets grinding the teeth out of the front one, and hand-made a tensioner for the belt drive.

Trevor then cleaned up an old Triumph four-speed gearbox from the 1950s he had laying around in his shed, modified a Suzuki clutch to fit, swapped the front-end out for a Kawasaki set of forks; no idea what the front wheel is from, it was just in the spare parts pile. Trevor then made a calliper to make it fit.

He added twin carburettors to each engine, and hand-made a custom splitter box to help make it easy to get full power when needed.

He then added a T140 disc rear wheel with Honda rear brake disc.

To make this baby go, Trevor went with a four-cylinder distributor that came of an old car. He modified it to fit in the front engine magneto holes with the firing order being front left, rear right, front right, rear left.

To top it off, he fitted a Sporty fuel tank and custom pipes and proudly carrying the MADE IN AUSTRALIA sticker. Most of the parts and engines are all from the 1950s and all the work was done in his backyard under the patio in the leafy suburbs of Perth.

Trevor would really thank his gorgeous wife Diane for all her support. Keep an eye out for them racing in the vintage scene. 

photos & story by Melody

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