Preunit Bobber: 1960 Triumph Bonneville 650

Preunit Triumph Bobber

Karl Ardo’s Preunit Bonnie Bobber…  

The original twin-carb pre-unit Bonneville 650 was a sales success, but Triumph had hurried the bike to market. The biggest deficiency was the single-downtube frame, which wasn’t quite strong enough to handle the added power of the Bonnie engine.

For 1960, the Bonneville (model TR7) received a raft of updates. Foremost was a new “duplex” frame with twin front downtubes, designed to correct the wobble that earned the old frame the nickname “Whip Iron.”  What’s more, the old DC dynamo was binned in favor of a modern AC alternator to keep the lights on — always a challenge with those pesky Lucas electrics — and the bike got standard Amal Monobloc carbs with integral float bowls for smoother running at low speed.

Preunit Triumph Bobber

This was still a pre-unit Bonneville — unit construction wouldn’t debut until 1963 — but Triumph was working hard to make the Bonnie the best it could be.

Preunit Triumph Bobber

Fast forward more than 60 years, and our friend Karl Ardo (@zerobalancer) got his hands on a 1960 Bonneville 650 — the original donor for the build you see here. You may remember Karl and his good friend / collaborator Josh Winderman (@thedayolds) from their resurrection of Todd Schuster’s “Tokyo Rose” CB750 drag bike for Born Free 13 — one of our most popular feature bikes, and a real gift to the motorcycle community as a whole.

Tokyo Rose, Reborn: A Legend’s Honda CB750 Drag Bike

For this build, Karl had in mind an old-school Triumph bobber like you might’ve seen rolling around Southern California in the 1960s — a British twin with nearly as much go as show.

Preunit Triumph Bobber

The bike is running 9:1 pistons with Triumph “Q” E3134 cams, matched with Amal 28mm monobloc carbs and a custom 1.75″ exhaust that seems downright mean.

The electronics have been upgraded to a 12-volt system with a Podtronics battery eliminator and Joe Hunt magneto.

Triumph Preunit Bobber

Up front, Karl installed a set of Benelli Phantom front forks with a Bultaco drum. Barring the Lowbrow Banana tank, most of the bodywork is handmade: oil tank, chainguard, rear fender, seat pan, exhaust brackets and brake stays, and more.


The paint is a custom mix laid down by George Tantardini of Hoodoo Speedworks, and Karl is quick to thank his good friend Josh Winderman (@thedayolds) for the fabrication work and Q&E Machine Shop for turning various parts for the build.

Fresh off a good buffing, the paint and polished aluminum look incredible in the California sun, and the long and low stance of the bike recalls the Triumph drag bikes of the era. Of course, the only thing better than looking at this beauty is the riding experience.

“A comfortable ride that handles effortlessly with a quick throttle response.” -Karl

Triumph Preunit Bobber

Below is our full interview with Karl about the build. Enjoy!

Triumph Preunit Bobber: Builder Interview

Triumph Preunit Bobber

• What’s the make, model, and year of the donor bike?

Triumph Pre Unit Duplex, Bonneville 650, 1960, matching numbers.

Triumph Preunit Bobber

• Why was this bike built?

Customer Project, I had total creative freedom.

Triumph Preunit Bobber

• What was the design concept and what influenced the build?

60’s Style Classic Triumph Bobber.

Triumph Preunit Bobber

• What custom work was done to the bike?
  • Lowbrow Banana gas tank
  • Oil tank and hanger
  • 1 3/4” custom exhaust pipes and support brackets
  • Rear fender
  • Airplane taillight
  • Fender stays
  • Rear brake stay
  • All aluminum rear brake hub assembly and spool
  • Chain-guard
  • Rear-mounted kickstand
  • 2 pan seat and cover
  • Benelli Phantom front forks
  • Bultaco front brake drum
  • Rare Amal 28mm monobloc carburetors with left and right bowls with custom side plates
  • 9-1 Pistons
  • Q-3134 cams intake and exhaust
  • Joe Hunt magneto
  • 12 volt high output 200 watt stator rotor
  • 12 volt 200 watt Podtronics battery eliminator
  • Custom mix red paint

Triumph Preunit BobberTriumph Preunit Bobber

• Can you tell us what it’s like to ride this bike?

A comfortable ride that handles effortlessly with a quick throttle response.

Triumph Preunit Bobber

Was there anything done during this build that you are particularly proud of?

The overall build ticked off all the boxes for me.

Triumph Preunit Bobber

• Is there anyone you’d like to thank?
  • This build could not of happened without the help of my good friend Josh Winderman and his amazing fabrication skills.
  • Q&E machine shop has always risen to the occasion.
  • George Tantardini aka Hoodoo, who painted the bike.
  • My vintage Triumph supply sources that always have what I need.

Follow the Builder

Karl Ardo: @zerobalancer
Josh Winderman: @thedayolds
Photo credits: Josh Winderman


  1. NICE!!!

  2. Andrew Cooper (Coup'e)

    Absolutely Awesome, beautiful color, beautiful style, Huge! biketastic…

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