Mix and Match: Norton Commando "Interback" Custom

Norton fan Jim Bush decided to make a Commando custom using only Norton factory components. The Interback is the result.

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1971 Norton Commando 750 "Interback"

Photo by Robert Smith

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1971 Norton Commando 750 “Interback”
Engine:
745cc air-cooled OHV parallel twin, 73mm x 89mm bore and stroke, 9:1 compression ratio, 58hp @ 6,800rpm
Top speed:
115mph (est.)
Transmission:
4-speed, chain final drive
Weight (dry):
400lb (182kg), approx.
Fuel capacity/MPG:
6gal (22.7ltr)
Price then/now (stock):
$1,595/$3,000-$13,000

When Jim Bush decided to take a stock Commando and turn it into a custom using only Norton factory components, he actually had quite a few to choose from: The Interback was the result.

Over its eight-year, almost 100,000-unit production run, the Norton Commando came in many different guises. All of them rolled on what was essentially the same chassis, drivetrain, suspension and wheels, with the later addition of disc brakes and electric start.

As our model-by-model call-out at the end of this article underscores, the differences were primarily in the bodywork, the handlebars, the exhaust system and the seats, all of which are easily removable and replaceable. That means Commandos are perfect for customizing, so could you create a unique, cohesive, custom Commando using only factory original parts? That’s what Jim Bush of Langley, British Columbia, wanted to find out.

The Commando “Interback” project

The Interback project started with a 1971 Commando Roadster. Bush first found the bike as a rolling basket case in 1994 and bought it with the intention of restoring it. It was advertised as “original, needs work,” but when Bush went to see it, he quickly realized it had been on the way to becoming a chopper before its owner lost interest. It had a beer keg gas tank, a tombstone taillight and the chain guard had been cut to allow a wider 16-inch rear wheel. It had been “stored” for 12 years, and the jugs had been “punched,” he was told. On the plus side, the frame, engine and gearbox were all matching numbers.

Bush got as far as getting the engine running, then consigned the bike to the back of his shop for later consideration. It languished there for a number of years as other projects took priority before he sold it to Tony Duffett in 2005. (Duffett’s Commando R was featured in the January/February 2008 issue of Motorcycle Classics).

Duffett completely dismantled the Commando and started on the engine, fitting a modified and gas-flowed cylinder head from Norton specialist Jim Comstock, high-compression pistons and performance 4S-grind camshaft, together with re-sleeved carburetors and a Boyer ignition. The stock timed breather system was augmented with a nonreturn PCV valve for positive crankcase venting to reduce oil leaks.

The bike wore stock Roadster bodywork plus a Corbin seat, but with special metal flake paint on the gas tank and side panels — applied by Jim Bush. Duffett’s Roadster was a show winner, taking first in class at the Tsawwassen, BC, Classic & Vintage Show ’n Shine in 2013. Sadly, Duffett passed away in December that year. “He called me in October from the hospice and asked me to find a home for his bikes,” Bush says. “I immediately said I would make a home for the ’71, and then found a home for the R amongst his friends.”

As a good friend, Bush knew the bike would always be “Tony’s” while it was still in its Roadster finish. So he decided to donate the gas tank to Duffett’s widow Laura as a memento, and he donated one of the side panels to a group of Duffett’s riding friends. “The purple metal flake takes some getting used to, and always had been identified as Tony’s bike, something I needed to respect; yet I wanted a daily rider that would still honor his meticulous work. The other side cover is on a stand in my shop as a reminder,” Bush says.

Blank slate

So Bush now owned a fully restored 1971 Commando without bodywork. Rather than build yet another stock Commando, Bush decided to set himself a challenge: Could he create a satisfactory custom Commando using only factory parts? The “Interback” was the result.

To start, Bush decided he wanted to use a fiberglass Interstate tank. Interstate tanks came in two sizes in steel as well as in fiberglass, the latter outlawed in the U.S. around 1973. “This was after ordering in an Indian-made metal Interstate tank. I found it was so poorly made that it had no place on the bike. It failed the 20-ton press test,” jokes Bush, “rendering it scrap.”

The seat originated on a Fastback LR, though Bush has shortened it by about 1 inch to accommodate the larger Interstate tank. The tailpiece is from a regular Fastback, and the side covers are from a Roadster.

Complementing the café look is a pair of headers from an SS model, fitted with mufflers intended for a 1972 Interstate. The finishing touch is a set of rearset footpegs from Norvil.

The result is a spectacular custom machine that looks like it came from the pen of a top Italian designer. The unusual combination of components looks just right — and works beautifully — and the 6-gallon gas tank gives a range of over 300 miles.

Most recently, Bush has also updated the Interback to provide a better “user interface,” with an electric starter kit from Alton. The Alton kit includes a new inner primary case that carries the starter. “The Alton starter works like a dream,” Bush says, noting that it was only “a two-hour install.”

Bush also fitted a Power Arc ignition system with switchable ignition curves, from Old Britts. “I wanted to make sure the voltage drop issues with the older generation Boyer were avoided to eliminate the possibility of kickbacks,” Bush says. “This has woken up the motor somewhat as well. It runs absolutely perfectly, and idles so smooth.”

For the future, a Norton-Lockheed disc front brake is in the plan to replace the original drum, combined with a sleeved-down master cylinder using a kit from RGM for extra stopping power. The smaller bore also improves brake feel. The front forks will benefit from a Lansdowne cartridge valve conversion.

“I love the comfort of the wide LR Fastback seat,” Bush says. “The rearsets put the feet in the right position, and an inch and a quarter chopped off each side of the stock Interstate handlebars makes it feel very comfortable on the arms. The high pipes and Interstate mufflers sound rich, with a nice bark!

“My plan was to build a modernized Norton, staying away from all the usual café bolt-on bits that abound on the Internet. With the disc brake, upgraded suspension, electric starter, comfortable seat, large capacity gas tank and tool storage in the tail piece, it will retain its classic character and good looks — and be a bike that is ridden.” Amen to that. MC


Norton Commando: Models Explained

Norton Commando Models:
1. The original 1968 Fastback
2. High-pipe S introduced 1969
3. One-year-only 1969 R
4. Roadster introduced in 1971
5. One-year-only 1971 SS
6. Hi-Rider introduced in 1971
7. 1971 Production Racer
8. Interstate introduced in 1972
9. 1974 John Player Special

The first Commando became known later as the Fastback. Shown at London’s Earls Court exhibition in September 1967, the Commando used a fiberglass gas tank and a tan-colored seat unit with “ears” that extended forward along the side of the tank. A tapered tail unit blended into the Lucas taillight. Mufflers were borrowed from Norton’s own Atlas, and the exposed oil tank (no side cover) was carried on the right side. Though many aficionados are unaware of this, the Fastback continued to be available until 1973, though by this time using the oil tank, side panels and peashooter mufflers from the Roadster.

The 1969 R used the basic Fastback layout but with a new fiberglass gas tank and a conventional seat. The 1969 S capitalized on the then-hot Street Scrambler look. The S moved the oil tank to the center of the frame, using triangular side covers to fill in the space. The seat and gas tank were from the R model. The S featured a chrome “halo” headlight ring, and a pair of chrome peashooter mufflers mounted high on the left side behind chrome-plated heat shields.

To many enthusiasts, the 1971 Roadster is the definitive Commando. It used the R/S gas tank, and a repositioned oil tank fitted behind the right hand side panel. The headlight was a conventional 7-inch unit and the header pipes fed into upswept peashooter mufflers.

The 1971 SS used a smaller “peanut” fiberglass gas tank, abbreviated dual seat, sprung front fender, smaller headlight and braced motocross handlebars. An elegantly curved waist-level header pipe ran along each side of the bike, terminating in short peashooter mufflers.

The 1971 Hi-Rider was a factory chopper for the U.S. market. It used the same “peanut” fiberglass tank as the SS and had high-rise bars and a backrest with a sissy-bar built into the seat.

The 1971 Production Racer was a limited-edition race bike with a blueprinted and carefully assembled engine featuring high-compression pistons, cylinder head modified for better flow, factory 3S race camshaft, shortened pushrods and larger valves, among other improvements.

The 1972 Interstate featured the tuned “Combat” 750cc engine with a claimed 65 horsepower, a 5-gallon fiberglass gas tank, new trapezoidal side covers and a shorter seat. Header pipes fed into slender “cigar” mufflers, kept low to facilitate the fitting of side luggage.

The limited-edition 1974 Norton John Player Special was a standard Commando 850 with bodywork designed by Mick Oilfield and inspired by Norton’s factory racers. An estimated 200 were built. A few were supposedly built with the short-stroke 750cc race engine used in the factory racers.

Only the Roadster and Interstate survived to 1975, the final year of full production and the last year for Norton in the U.S. — Robert Smith