Bikernet Blog Search Bikernet
Ride Forever -
Thursday Edition

The Pre-Unit Triumph Bobber Mantra

Bryan Thompson Reaches for Traditional Refinement

By Wrench with photos by Peter Linney

Share this story:

Bryan Thompson took on this build like a mountain man with a mission. He had to build a pre-unit bobber and stay true to the Triumph code. Only Triumph components could be used.

No custom frame, forks, or wheels; just a couple of traditional Bates components and the rest original.

But let's back up first. Bryan has been a two-wheeled guru since a teenager, when he took bicycles apart and painted them. Then he moved on to Vespas, until he fell in love with speedway racing in Costa Mesa, Caifornia, and hammered the dusty track for years until his body cried for a reprieve. Then his vintage blood surfaced.

"I always admired BSAs and Triumphs," Bryan said. He took on a rough '66 Triumph bobber.

"But the pre-unit Triumphs had the look I was after," Bryan said. He did his research and discovered later '50s Triumphs contained better power, improved gear boxes, and refined clutches. He started his search.

"Thank God for swap meets," Bryan said. "Ebay drives up prices, and you can't tell anything about what you're getting." He ultimately found the '59 frame, motor, and rear wheel at a swap meet.

He wanted the performance of the later model Triumph, but the style of the rigid. He found a stock '52 rigid section and stretched it slightly so he could run the '59 Triumph oil bag. But he made a special effort to ensure that every aspect appeared as if it was stock. He didn't want any welds to show, so after welding, he hand-ground, then filled, and ground some more. No welds show and no Bondo was used.

He rebuilt the engine and added the Bonneville head for additional performance. He's always enjoyed painting, but shooting House of Kolors candy was a new and daunting experience.

"There are over 15 coats of paint used during the finish process," Bryan said. He started with House of Kolors primers, then sealers, then base coats, candies, clear coats, then graphics, gold leaf, pin-striping, and more clear coats.

The master and his rider.
The master and his rider.

At one point, while attempting to use environmentally friendly paints, he cleared the rear fender, and left it to dry in the shop under heat lamps. It didn't dry for hours. He hauled it outside, and it still didn't dry.

"I took John Kosmosky's House of Kolors class," Bryan said. But he forgot to add the hardener to the final clear coat. Very carefully, he cleaned the unsetting clear coat off the fender with thinners, re-mixed his clear concoction, and the fender survived.

This is one of the finest custom Triumphs we have ever run across, and his show awards prove it. Next, he will enter the San Jose, California Clubman Show devoted to British bikes.

Bikernet Magnificent Triumph Tech Chart

Owner Bryan Thompson
City: Arroyo Grande
State: California

General Info

Make: Triumph
Year: 1959
Model: TR-6 pre-unit
Type: Bobber
Fabrication: Owner
Time: 5 years
Assembly: Owner


Type: TR-6
Displacement: 650 cc
Year: 1959
Pistons: Stock
Cylinders: Original
Head: Bonneville dual-carb
Camshaft: Stock
Lifters: Solids
Carburetor: Amal Monoblocs
Air Cleaners: Dual velocity stacks
Exhaust pipes: Straight, minus mufflers


Type: Original rigid
Year: 1959
Builder: Triumph
Stretch: Stock
Rake: Stock
Swingarm: Removed and replaced it with '52 hardtail
Mods: Swingarm extended


Molding: On frame, seat brackets and fender
Painter: Bryan Thompson
Color: Candy Apple Red, House of Kolor
Lettering and gold leaf: Dave Bond, Lucky B Design
Powder coat: Rear hub--chrome, taillight bracket--gloss black


Type: Triumph glide
Year: 1959
Rebuilt by: Owner
Trees: Stock



Size: 21-inch
Rim: Triumph
Hub: 1952 Triumph
Builder: Buchanan's
Finish: Chrome by AC Plating, Bakersfield
Tire: Avon Speedmaster
Brake: stock drum


Size: 18
Rim: Stock Triumph
Brake: Stock drum
Builder: Buchanan's
Finish: Chrome by AC
Fender: Ribbed Bates
Tire: Indian
Hub: Stock


Handlebars: Old parts
Risers: Stock
Headlight: Bates
Taillight: Vincent
Seat: Modified Bates
Oil Tank: Pre-unit 1952
Fuel Tank: Triumph from the '60s

Special Thanks: To Mickey Peter

Share this story:

Back to Bike Features

Reader Comments

Hi. Can anyone tell me where the battery box/Cover on the other side of the oil tank comes from?

Aarhus , Jutland, Denmark
Thursday, July 20, 2017
Editor Response I'm looking into it. I think they were stock units from different models. Still looking.
Bitchin bobber. I absolutely love it!!!
(The model isn't shabby either)

Red Deer, AB, Canada
Sunday, May 11, 2014
What make and model tire is on the back of this triumph. Nice job


Friday, May 9, 2014
Editor Response Good question. The chart says Indian. The front is an Avon. You might check their vintage line-up first. Tell 'em Bikernet sent you.
Wow... now I remember why I love Triumphs.

Von Frost
Long Beach, CA
Monday, March 12, 2012
Editor Response What a beauty.

Your thoughts on this article

Your Name
Anti-Spam Question:
Please enter the words you see in the box, in order and separated by a space. Doing so helps prevent automated programs from abusing this service.