Motorcycle Classics

Yellow Peril: Norton Commando Production Racer

1971 Norton Commando Production Racer
Top Speed:
131mph (period test)
Engine: 745cc air-cooled OHV parallel twin, 73mm x 89mm
Weight (dry/est.): 400lb (182kg)
Fuel capacity/MPG: 6gal (22.7ltr)/4.2gal (16ltr) stock
Price then/now: $1,900 (est.)/ $5,000-$14,000

The devil is in the details, they say. That certainly applies to racing motorcycles. It’s not just bolting together go-faster bits that wins races: It’s also the painstaking task of squeezing out more performance by incremental improvements; reducing friction and saving weight; blueprinting and matching components; machining, shaping, honing and polishing.

Take the Norton Commando Production Racer, for example. Though it certainly included some special performance parts, the engine wasn’t that far from a stock Commando. But by careful tuning, testing and assembly, the factory race department was able to find at least a dozen more ponies than a stock Commando. And it didn’t hurt that the competition shop had its own full-size test track!

Plumstead to Andover

The Production Racer story really starts in 1969 with the pending closure of the old AMC factory in Plumstead, London, where most Commandos were assembled at that time. The site was slated for development, and the company issued a compulsory purchase order. But as part of the deal, Norton-Villiers (the company rebuilt from the ashes of AMC by new owners Manganese-Bronze Holdings) acquired new premises in Andover, Hampshire, on the site of the Thruxton racetrack. As well as a Commando production line, N-V chief Dennis Poore established a race shop at the new site under the guidance of ex-AJS racer and development engineer Peter Inchley.

The Thruxton airfield had been a bomber station during World War II, and Inchley’s workshop was a converted B17 hangar — re-christened the “Long Shop.” And of course, it helped having the Thruxton circuit on site as a development testing ground. Not only that, but by 1970, Inchley’s team included one of the world’s best development riders, Peter Williams.

It should come as no surprise, therefore, that the Commando Production Racer’s first major victory was in the 1970 Thruxton 500 mile race with Williams and Charlie Sanby riding. Williams came within 1.6 seconds of winning the Isle of Man Production TT that year, too, but ran out of fuel just before the finish. That allowed Malcolm Uphill to take the trophy on his Triumph Trident. Clearly, though, the Commando Production Racer (CPR) had plenty of potential. 1971 saw Williams finish third in the Formula 750 race on the Island, while setting a new lap record of faster than 101mph in the 750 Production race before retiring.

Hand-assembled racer

The CPR was offered for sale to privateers who wanted to compete in production-based 750cc racing, and it quickly became the premier choice. But outright victories were hard to come by. Reliability of the extra-stressed powertrain was an issue, with gearbox failures being particularly prevalent. The humble Norton gearbox, though extensively improved during the AMC years, had its origins in the 1930s, when it was intended to handle maybe 20 horsepower. With a good Production Racer making more than three times that — about 70 horsepower — failures were almost inevitable.

Although it came equipped with lights and was fully street legal, the CPR was never intended for the street. At roughly $1,900, the price for potential glory wasn’t cheap. At the time, a new Honda 750 Four cost $1,495, a stock Commando sold for $1,479, and you could buy an Austin Mini for less than $1,500!

Whether or not Norton made any money selling Production Racers, even at their high price, is moot. The incentive for building CPRs in quantity wasn’t to make money, but to gain homologation under FIM and AMA for racing under “production” rules.

But what did the average buyer get for his extra money? Quite a lot, actually. Inside the engine went higher compression pistons and the factory 3S racing camshaft, while the cylinder head — individually selected from standard molds, as were the cylinder barrels and engine cases — was modified for improved gas flow and the squish bands were machined away inside the combustion chamber. Special shortened pushrods operated bigger diameter valves in phosphor-bronze valve guides via polished rockers. Blueprinting and matching components together (the aluminum connecting rods were matched) with fastidious assembly completed the package.

To the basic CPR specification, customers could specify 32mm Amal GP or Concentric carburetors, and the newly available Boyer-Bransden electronic ignition instead of mechanical contact breakers. Primary drive was stock Commando with a diaphragm-spring clutch. A close-ratio 4-speed was standard, though a 5-speed gear set from Rod Quaife was also an option.

While the frame, engine cradle and Isolastic mounts were stock, the front suspension was re-valved and fitted with new fork legs, the left side including a cast-in carrier for the Lockheed disc brake caliper. The wheels were special, too. Testing had shown that a narrower front tire improved lap times, so the CPR used a custom Norton front hub, spoked to a Dunlop WM2 2.5-inch alloy rim with a 3.60 section tire. At the rear, a WM3 alloy rim was wired to a custom ventilated 8-inch brake drum. (Stock Commandos used steel 19-inch Dunlop WM3 rims front and rear.)

Other modifications unique to the Production Racer included omission of the sidestand lug on the frame, the oil tank modified to clear the seat unit, ignition switch centrally mounted behind the engine, ammeter mounted on the steering yoke and the frame I.D. plate mounted under the seat instead of on the headstock. Most noticeable, though, was the 4.2 gallon (U.S.) aluminum gas tank, the special seat unit and the bikini fairing, all finished in bright yellow. Production Racers soon earned the nickname “Yellow Peril.”

From 1972, the focus of Norton racing changed, while on the production side, the company was dealing with the Combat engine debacle. New sponsor tobacco giant John Player & Sons was less interested in production racing and wanted Norton to compete in big name events like Daytona and Imola. Peter Williams never did win a Production TT with the Yellow Peril and victory on the island would have to wait until 1973, when Williams was first home in the F750 race with the “monocoque” (really a twin-spar peripheral frame) Commando-engined John Player Norton (see John Player Norton Commando).

Because of their special components and meticulous assembly, CPRs have become perhaps the most collectible of all Commandos. And with fewer than 200 built, finding one isn’t easy. Chances are good any survivors have been raced, but if you do find a nice one, it’s likely to be a pretty solid investment.

Ron Baillie’s Norton Commando Production Racer

Ron Baillie of Campbell River, British Columbia, Canada, is convinced the bike he rescued from under a workbench in Vancouver is the real deal: a genuine 1971 Commando Production Racer.

First, the engine and frame numbers match — not that the CPR was unique in that respect, but it helps. Ron has also determined his bike was built in March 1971, which fits with the 20M3S-type engine. And Ron has copies of a sales transaction made in 1972, which fits with the bike having been sold later as a “project” in 1979, before it languished in a heated warehouse in Vancouver for the next 33 years.

The engine had suffered a major blow-up, Ron says, and had then been reassembled using stock Commando components — though the special short pushrods were still in place: a major clue.

Ron has now fully restored the bike using the correct CPR engine components, while most of the other special CPR items were still with the bike. The only non-CPR items are the Norvil rearset foot controls and marine-quality oil, gas and hydraulic lines.

Ron’s bike certainly ticks the boxes as far as equipment is concerned, even down to the oil tank having been “modified” (the top flange had been ground down, as they did at the factory) to fit under the special seat. Though Amal GP carburetors could be specified and a 5-speed gear cluster was an option, Ron’s bike wears Amal Concentrics and 4-speed tranny.

Is it genuine? Opinions vary. Somewhere between 100 and 200 Yellow Perils were likely produced, and like many limited edition motorcycles, more seem to exist than were made.

In theory, it should be possible to confirm a CPR’s origins from production records, which the Norton Owners Club now claims to hold. However, every CPR was built in the race shop, not in the factory, so the records may not be complete. Andover Norton parts company claims to have obtained microfilm of the relevant dispatch records, which should be conclusive. But the bottom line is, if you’re offered a “genuine” CPR, the usual caveat emptor applies.

So is this a genuine, factory prepared Commando Production Racer? Ron certainly believes so, and on the balance of probabilities, he has a pretty strong case. But it would take a real expert and some intensive research to confirm beyond reasonable doubt. Either way, it’s a beautiful restoration and a fitting tribute to the Norton factory’s success at keeping the Commando competitive beyond its prime. MC

For more on Norton Motorcycles read Production Racer: Norton History.

  • Published on Oct 8, 2013
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