This Norton is neither practical, economical, durable nor reliable. It is, however, loads of fun. Even the editor has been glimpsed grinning after a brief ride around the industrial Welsh wastelands. Subsequent attempts to charge his dental bills against my fee for writing this have been firmly resisted. The-poor state of the editorial teeth are blamed rather than excessive vibes from the world's largest production vertical twin.
The stock Norton 850 engine has always been a relatively mild device, with a mere 55hp. Norton achieved notoriety in the early seventies by marketing the wildly tuned 750 Combat engine. Needing a new set of main bearings every 500 miles didn't win too many friends. But did it shift. The raw and nasty power of a big vertical twin on cam is somehow much more satisfying that the slick, smooth acceleration of even the latest multi cylinder highway hoodlum. The plan was to combine the performance of early bikes with the improved strength of the later 850.
The result is a bike that accelerates as fast as anything else on the road. Engine life is extended to 5000 miles. Possession of a spare engine means that the bike is only off the road for an afternoon. Engines can then be rebuilt at my leisure, usually when the rain, snow or freezing temperatures make riding the Norton impractical.
Both engines are in a similar state of tune. The maximum amount of power is extracted from the design by the usual methods of increased compression, wild cams, large valves and free flow exhausts and carbs. Compression ratio is around 10:1. Cams are modified Combat units that have been re-welded and machined to an even lumpier spec. Carbs are 34mm Amals without filters. The exhaust was rescued from the race track, its short two into one form sprayed matt black. The rockers, pushrods and pistons are lightened and polished. Crankshaft and conrods are stock Mark 3. Standard triplex primary chain and multi-plate diaphragm clutch are retained. The 4-speed box is standard and hasn't been touched in 30000 miles.
To achieve decent power, and retain a semblance of reliability, meticulous care and attention in engine assembly has to be observed. There is no room for that subtle kind of engineering where mole-grips and large hammers are the main tools. Because of the pre-unit design, the engine is extremely easy to work on and can be shifted around without causing hernias.
Using a ridiculously long stroke (89mm) means the con-rods are always subjected to huge forces at high revs. Standard rods last about ten thousand miles. They are carefully polished between rebuilds. Many special rods are available, but they are far too expensive for mere mortals. New main bearings are fitted every 5000 miles, and the crankshaft has to be completely rebuilt every 10000 miles. While the cams last for ten grand, the rockers, tappets and pushrods all need major attention at each rebuild. Rebores are needed every 15000 miles and new rings every 10000 miles . Exhaust valves are reground at 5000 miles, while inlet valves last twice the distance. The heavy duty valve springs are replaced every 10000 miles. Primary drive and clutch plates all go for all of fifteen grand before needing replacement , A lot of hassle, maybe, but rather more fun than wasting evenings watching TV.
All this effort produces around 65hp at 7000rpm. And these are real horses that sweat oil and scar metal before making it to the back wheel. Enough power for an indicated 135mph, and the kind of acceleration that will have Porsche owners weeping into the hands of their dealers. Up to the ton the bike has blown off the latest high tech bikes, and seen off some very highly tuned large Jap fours. They just can't match the sheer grunt of the Norton. Beyond 100mph life is a little more sedate, but then without a fairing such excessive speeds can't be maintained for any length of time.
The stock chassis is famous for suffering poor stability in corners when the throttle is backed off. The engine, gearbox and swinging arm are rubber mounted in a tubular frame, gaining most of its strength from a large diameter tube between steering head and saddle tubes.The amount of free play between swinging arm and frame is determined by shimming up the Isolastic mounts. Improved stability can be attained by reducing the clearances to zero. This increases vibration at certain points in the rev range. The shims need re-adjusting around every 5000 miles to maintain decent handling. This is a tedious and time consuming process needing plenty of patience and concentration. Unfortunately, neglect leaves the Commando uncontrollable on bumpy country roads .
Weight of the already light Norton (430lbs) has been further reduced by fitting GRP petrol tank, seat and mudguards, as well as a two into one exhaust system. With a gallon of petrol, the bike weighs in at just under 400lbs. This helps the ease of handling in town and country, without any instability occurring during motorway riding. It's still no comparison to the old Featherbed frame Nortons, which can still see the Commando off down country lanes, where the improved power can't compensate for the inferior chassis. The Commando just doesn't have the lightness of touch and steering precision present in the older bikes. The Commando is as stable as the slower Bonneville, but doesn' t quite match its agility. Older Jap fours are burnt off with relative ease but the newer, sophisticated mobjust show the brutal effects of the progress of motorcycle design. If zero clearance is maintained, the Norton avoids anything as frightening as a speed wobble.
At tickover the engine shakes about in the frame in an alarming manner. Tremors affect tank, seat and handlebars. This becomes worse up to 30mph, when the bike becomes relatively smooth. Above 70mph, in fourth, the vibes start to intrude. Increasing speed increases the vibes, until by the ton everything has become hopelessly blurred and rather frightening. Once past the ton, the Norton smooths out somewhat. It's still harsher than the secondary vibration from a large four, but it's a definite improvement over other British twins at similar speeds. Riding flat out with the rev counter gyrating between seven and eight grand brings out all the inherent nastiness of large vertical twins. This can be absorbed for a few seconds, but anything above 120mph is a quick route to a terminal mechanical accident.
Because the Norton represents a considerable investment in time and money, such high speed jinks are restricted to the occasional moments of madness. The Norton is usually used in anger when rushing around central London, or as our editor would have it, Shit City. The combination of low mass, massive torque and narrow build makes it an ideal device for putting LC owners in their proper place. The combination of a single disc brake at each end is well suited to avoiding taxi drivers and pedestrians. Although, the standard SLS rear drum probably represents the ultimate in rear brakes. Still, the discs combine power and sensitivity with the ability to stop the bike in the wet. Wimps may not like the amount of pressure required to operate the front brake, but Nortons have always been bikes for real men.
The exhaust system is devoid of any baffles. It is loud enough to penetrate even the most luxuriously appointed car interior. Acquaintances inform me that their car radios are rendered inoperative, and that dogs go beserk when the bike is anywhere within half a mile of their presence. The 'silencer' length is apparently half the length of the stock system, which keeps the harmonics of the exhaust somewhere in line with the combustion pulses making their way through the engine. The system works well with the large carbs and wild cams. At low speeds in top gear the engine is a muted growl, which grows into a soul inspiring wail once on cam. This is one of the few advantages of having pistons that move in unison. The exhaust system will be replaced by a socially acceptable unit just as soon as car drivers begin to use the road in a socially acceptable manner.
In comparison, the stock horn is lost in the heady mixture of exhaust and engine noise. Experiments with quartz halogen headlamps were quickly forgotten when vibration kept blowing the bulb. Standard lights are barely adequate, but are resistant to the vibes. The rear bulb blows every 1200 miles, despite the use of an old inner tube to effect some additional rubber mounting. Stock Lucas alternator feeds a radically altered electrical system. Electronic ignition replaces contact breakers famous for an advance and retard unit that malfunctions, altering ignition timing and holing pistons. The 10 amp/hr battery is thrown away because it doesn't last for more than six months. Energy Transfer Ignition (a big capacitor in place of the battery) takes its place. The unreliable Lucas rectifier and Zener diode are also thrown on the scrap heap, replaced by stronger items out of a car accessory shop. All of these modified electrics are combined on a rubber mounted aluminium plate, with one electrical connector for ease of replacement. The system needs a new capacitor every 12000 miles. A modified circuit now allows for a spare capacitor to be utilised at the flick of a switch. These components were all acquired for less than ten quid.
The most exciting moment of ownership comes when attempting to start the beast. This can only be done on the centrestand, because all the rider's weight and force are required on the kickstart . With the engine just past compression and the carbs tickled, no choke and no throttle, a brave kick is needed. With wild cams and timing, the engine can spit back through the carbs. or kick back through the kickstart. With a little practice, it usually comes to life on the second kick from cold. The engine stutters into life, needing a quick handful of throttle to stop it from dying. It takes at least a minute until the motor settles down to a regular tickover. Once warm, the engine starts first kick, although it does have a greater tendency to kick back. I always aim to let my foot slide off the kickstart just before the end of its travel to avoid breaking my ankle. If you've never owned a big twin before, this Norton would probably give you a lot of trouble.
I favour either Roadrunners or TT100s, as the frame is stiff enough to use these tyres to their best advantage . Tyre wear would give the editor a coronary. Either make of tyre is down to 2mm at the rear by only 3500 miles and the front lasts for little more than five grand. Both wheels are fairly easy to remove for tyre replacement. The chain fares little better, needing replacement somewhere between three and four thousand miles. Running on a worn chain adversely affects the normally smooth and precise gear action. Using worn tyres sets up a mild weave above 75mph. This turns into a speed wobble if the front tyre is worn right down and the road has a bumpy surface. Both front and rear brake pads are replaced every five thousand miles, but they only cost five notes a set.
Fuel consumption varies between the awful and the really awful. One high speed run, in the company of some speed addled maniacs on Rickman-framed Kawasakis increased consumption to 25mpg. But it was rather good fun. Shit City commuting returns between 30 and 35mpg. The best consumption, when running in some new pistons, was 40mpg. And, yes, I know your Kawasaki GPz900 will average that while cruising at the ton. We're talking the joys of British motorcycle ownership here , sonny.
If I was ever to count the true cost of running this Norton, I'd probably end up selling the thing in pure frustration. It needs too much time and attention in comparison with most other bikes on the road. Regular servicing every 500 miles, and an engine rebuild every 5000 miles, are only for the dedicated. But I've tried most other bikes on the road, none of them can compare with the way the rorty old Norton delivers the goods. The design of the engine is ancient, the chassis is dubious , the suspension ten years out of date, and the brakes hardly up to modern spec. And yet, out of the road where it really matters, the Norton is very much alive and kicking, willing to take on even the most modern bikes. Anyone want a race?
Johnny Malone