Twin-Engined Triumph Bonneville


1974 Triumph Bonneville

Steve Pieratt’s amazing twin-engined Triumph Bonneville. It’s long, but it still looks like a Bonnie.

The annual Barber Vintage Festival is always full of surprises. Interesting, odd and downright weird classic and vintage bikes seem to come out of the woodwork for this annual celebration of all things motorcycle, including machines like Steve Pieratt’s incredible twin-engined Triumph Bonneville, which Steve entered in the Motorcycle Classics Vintage Bike Show at the 10th Annual Barber Vintage Festival in 2014.

Based on a 1974 Triumph Bonneville 750 T140, Pieratt’s bike has been extensively modified to accommodate a pair of 750cc Triumph twin engines seamlessly mated together, resulting in a 4-cylinder, 1,500cc Triumph Bonneville. The two engines share a common primary drive, which couples the front engine (which has had its transmission surgically removed) to the rear engine. The rear engine retains the stock Triumph T150 5-speed box. The primary cover was created by grafting two stock covers together, welding and shaping them to the desired profile, followed by final polishing. The finished cover is a work of art and looks like it came out of the Triumph factory. A polished stainless steel plate couples the two engine case together on the right timing cover side.

1974 Triumph Bonneville

A close look at the engine shows a pair of stock primary covers welded and formed together; they almost look factory.

4/13/2015 8:48:18 AM

I first saw this beautifully built Triumph in 1998 at the AMA Vintage Days, Mid Ohio Motorsorts Park. My photo album includes this bike for sure! It looks just as good today as it did then. Great engineering and I'm jealous of Richard for getting to enjoy the fruits of Steve's labor! American ingenuity can't be beat!!!

4/9/2015 2:56:39 PM

The question to ask is how does he keep the rear engine's exhaust valves from melting? Many before him have tried rear-facing jugs of one sort or another, and to my knowledge, an overly hot exhaust has been the death of most of them.

4/9/2015 10:00:22 AM

It appears that a '70 front end has been used. Can you give us a few details on frame, front end, wheels, brakes, etc.?

The sound and the fury: celebrate the machines that changed the world!

Motorcycle Classics JulAug 16Motorcycle Classics is America's premier magazine for collectors and enthusiasts, dreamers and restorers, newcomers and life long motorheads who love the sound and the beauty of classic bikes. Every issue  delivers exciting and evocative articles and photographs of the most brilliant, unusual and popular motorcycles ever made!

Save Even More Money with our RALLY-RATE plan!

Pay now with a credit card and take advantage of our RALLY-RATE automatic renewal savings plan. You save an additional $5.00 and get 6 issues of Motorcycle Classics for only $29.95 (USA only).

Or, Bill Me Later and I'll pay just $34.95 for a one year subscription!

Facebook Pinterest Instagram YouTube Twitter