by Rod Ker

Rod Ker finally gets to try the Commando properly and enjoy the fruits of his labour – he’s even sussed the clutch. Read on…

This is probably the last chapter of the Commando Saga, you will all be relieved to hear. As I write, the bike has been on the road, taxed, tested and leaking oil for about six weeks now, so the ‘restoration’ is complete. However, as most of us appreciate, keeping an old British clunker on the road is really a Forth Road Bridge painting type of exercise. As soon as one bit is fixed, another bit needs attention!
Nothing serious has happened since the Norton first belched back into life again. As related last month, the only problem has been the clutch, which has now been apart about six times. When first put together, it worked perfectly. Then, slightly mysteriously, after about half an hour or so of running, it suddenly began to drag badly – so badly that it was virtually impossible to change gear, or stop, for that matter.
Naturally this only happened when I was about to take the bike to a pre-booked MoT test, which led to a slightly embarrassing first trip. The engine seemed fine, it was just that as soon as I got stuck in traffic I looked like an out-of-control CBT recruit. So, after stemming the oil leakage from the tappet covers, I stripped the clutch down and investigated, expecting to find something blindingly obvious wrong. But there wasn’t. The plates were all flat, the clutch centre and outer drum weren’t too worn, and the lifting mechanism was working perfectly.
Seeking advice from others opened a veritable can of worms: everyone had a pet theory about how to make Commando clutches work properly. If you have a day or two to spare, try entering ‘Commando clutch’ into an internet search engine and following the links. Vast difference of opinions, from all over the wired world, surely they couldn’t all be right?
The basics are that Norton decided to use a car-type diaphragm spring instead of the more normal set of coil springs to hold the plates together.
That explains the clutch’s slightly odd ‘over-centre’ feel as the lever is pulled in, but doesn’t really have much to do with all the other fun and games people seem to have in trying to make it function. Either it slips or it drags, or both.
Early models had what are commonly referred to as ‘postage stamp’ plates, where the friction material is arranged in a radial pattern of square-ish blobs, as per normal bike practice. Later bikes like my MkIIA were originally fitted with a set of all-metal friction plates, made of a bronze material similar to that seen in fork and gearbox bushes. Keen readers of ancient motorcycle magazines’ ‘Get You Home’ hints will appreciate that in the latter case there’s absolutely no chance of rummaging around in pub dustbins for bits of cork to jam in the plates. If the bronze plates are flat and of the correct thickness, what could possibly go wrong? Plenty, is the answer.
Aside from the type of friction material used, there are variations on how many plates are fitted, and the thickness of the pressure plate. Then there’s oil to consider: my Haynes manual recommends using the same 20/50 in the chaincase and engine. Others say 10/30, while the most popular choice nowadays is Automatic Transmission Fluid, which is thinner still, probably about 5W. You also have to remember that some Nortons converted to belt drive don’t have any oil in the chaincase. Or at least, they don’t until the gearbox performs its special magic and pumps horrible thick EP90 along the clutch pushrod and sprays it around.
My clutch didn’t slip, but it dragged enough to ruin the gear change and make selecting neutral a challenge. I’d already checked all the usual suspects – warped plates, lifting mechanism, etc – but had initially put ordinary 20/50 in the chaincase, because Mr Haynes’s word is gospel (ho, ho). The first thing to try, then, was refilling with ATF, after scrubbing the plates clean in solvent. Petrol does the job, but it’s not PC to recommend using it these days. Everything should be fine if you don’t work by candlelight, though.
This improved matters more than expected, although the clutch seemed a touch inconsistent in operation. Translation: I either stalled it, or sat looking stupid with the engine at 6000rpm, going nowhere. Neutral was still completely theoretical, of course.
Being a glutton for punishment, I then believed something I’d read on an American Internet site, written in such an authoritative way that it simply had to be true. The secret was to remove one of the steel plates, Alvin B.
Smeghead Junior the Second, stated, categorically. As I’d done this before on other bikes with some success, it seemed worth a try. Yet, my confidence in this ruse waned rapidly once I’d started putting the clutch back together, and seen that the diaphragm spring was exerting hardly any clamping pressure on the stack of plates.
Well, it worked – sort of. The clutch freed off perfectly and didn’t show the slightest sign of drag. Gears shifted like knives through cliches. Neutral snicked in like a dream. Great. The catch was that as soon as the engine started producing that famous ‘lotta torque’ (as the US ads used to say, but possibly when Alvin B etc was still in kindergarten), the clutch just let go completely. It also began slipping when trying to kick the engine over, which is potentially a very silly way to find yourself stranded with an unstartable bike, as I once discovered on another old Brit, many moons ago.
On that occasion I seem to remember having to take one of the sparkplugs out and limping home on an extremely noisy single. This time I managed to coax it back to life, but had extreme difficulty getting up a hill and finished the journey with moped-like performance.
Ever the optimist, I did try to convince myself that the extra wear caused to the friction plates in this interlude would have reduced the height of the plate stack and might possibly make the clutch less draggy. Funnily enough, after another stripdown, plate-clean and reassembly, this did seem to be the case. The clutch worked acceptably – at least as well as it does on many other ancient bikes that are supposed to be in fully functional order, in fact.
But I knew it could be better, so after a week or two of occasionally crunchy progress I made another visit to Norvil for some sage advice, plus the parts to make it right. Once again, the cure was simple: bin the five bronze bacon slicers, then fit four Surflex friction plates, adding an extra steel plate to achieve the correct stack height. That stops the clutch slipping or dragging except when it’s supposed to, but in order to keep it that way you have to stop EP90 from the gearbox dribbling along the mainshaft and contaminating the chaincase oil. This is done by fitting an O-ring, cleverly located in a housing that screws onto the end of the mainshaft, outboard of the clutch nut. Simple... And it works.
At the same time I also fitted a Norvil one-way valve to the engine breather, which should result in lower oil consumption (from both leaks and burning by recycling through the air-filter) and extra bhp. All you do is cut the hose near the battery tray and install the big brass gizmo in the break. Must be the most instant go-faster aid yet!
So – back on the road to do some more running-in miles, upping the pace gradually as the new parts bedded in. Although it was a relief that the engine was sounding happy and performing well, the throttle slide on the right hand Amal redeveloped its habit of sticking open slightly, which spoiled the ride. The annoying thing was that it only happened intermittently, and never when I was near a toolbox.
The points gap and/or ignition timing also felt as if it was beginning to suffer slightly from Lucas drift. Yes, I know I should throw the contact breakers and wobbly mechanical centrifugal advance unit away and fit a Boyer electronic system, as promised in an earlier instalment. It will happen, honest! For the moment, though, I’ve decided to leave it alone. The engine still starts first kick, cold or hot, and doesn’t pink or show signs of overheating, so I doubt the Boyer would make a huge difference, at least until it’s fully run-in and ready to take a bit more stick.
My other plan to fit ‘peashooter’ silencers has also been temporarily forgotten. I have to admit that in my old age the relative hush provided by the giant ‘black cap’ cans is quite appealing. Besides, the baffles in one side seem to be falling apart gradually, so it probably won’t be long before the bike rattles windows like a ‘real’ Commando!
Before that happens, I’ve been cruising around in silence, marvelling how Norton managed to make such an old engine so smooth and refined. The vibration is still there, of course, but the Isolastic system kills it before it gets near the rider. Thinking about this, I was reminded of a feature in the American magazine Cycle, which I read as a more interesting alternative to school work, many moons ago. ‘Eight for the Open Road’, the story was called, and it just so happens that I have a copy to hand.
The idea was to bring all the 1975 crop of large-engined bikes together, rating them on key points. The protagonists comprised BMW R90/6, Honda Gold Wing, Suzuki RE5 rotary, Moto Guzzi 850, Harley Electraglide, Suzuki GT750, Kawasaki Z1B and (hurrah!) a Norton 850 MkIIA Interstate, just like mine. In the Overall Noise Level category, predictably, the GoldWing scored 9, with the BMW some way behind on 7.8. Still more predictably, the H-D earned a pathetic 1.7, one of many humiliations. But, against all the odds, the Commando came third with 6.1! It also finished fourth for Vibration Control, with another 6.1 score. In the final reckoning the Norton came a less impressive sixth, dragged down by low marks for Quality of Workmanship, Maintenance/Convenience and Two-up Comfort.
All of which I’d agree with entirely. Apart from making one wonder why it is that 28 years later no modern-bike magazine seems able to put together a feature half as interesting and informative, the thing that amused me was how Norton beat Kawasaki in a few categories. I can’t imagine anyone ever deliberating between an Electraglide, GoldWing or BMW and a Commando – the real killer for the Brits was the arrival of Japanese bikes that went much faster. ‘King’ Z1, over $400 cheaper, yet 1.7 seconds quicker over a standing quarter, was really the final nail in Norton’s coffin.
So, I thought, how about a little comparison testette in 2003? Finding a mint Z1B to pit against my ditto (but by this stage lightly patinated with oil and squashed flies) Interstate was easy. Seventies Kawasaki specialist, RWHS Classics (01630 657156, www.classicbikes.co.uk), is only half a gallon of LRP away. Back in 1975, the blue example seen here might have been standing alongside my Commando in a showroom. Whatever the US list prices, here in Blighty the MkIIA tended to be available at a generous discount (well under £1000), especially once the electric start MkIII arrived on the scene.
Where the Kawasaki scores most over the Norton is in its convenience and ease of use. Flip the choke lever, press a button, and you’re away before the Commando pilot has managed to get the key in his ignition switch cunningly hidden behind the leaky fuel taps and incurably incontinent Amals. Even if the carbs didn’t weep, you deliberately have to force them to overflow for a cold start, a messy practice that would shortly be outlawed in America.
Once running, the Norton regains ground in some areas and loses it in others. The Isolastics only work properly past about 2500rpm. Below that, low-frequency shudders make life unpleasant. At some speeds/revs the shakes make your eyeballs jiggle enough to interfere with vision. No, I’m not joking. Incidentally, you get exactly the same effect on current Buells, which rely on a similar anti-vibration frame system called Isoplanar.
On my bike the low-speed ride is also spoiled by the front wheel, which is less than 100 per cent round, making the steering flutter a bit. A spoke tweak should hopefully improve matters, but unless it suddenly gets worse I’ll carry on ignoring it. Meanwhile, the rear tyre, fitted to a circular wheel, has worn remarkably quickly considering how slowly I’ve been going. Despite these handicaps, the handling is pretty confidence-inspiring. I reckon I could ride the Norton faster round most bends than the Kawasaki. Cycle magazine thought so too, rating the Commando second for mountain roads handling. The Z1 was only narrowly beaten into third place, though. And the winner? Nope, it wasn’t the Electraglide. Strange but true, the Suzuki RE5 actually came out miles ahead of the rest!
In a top gear roll-on the venerable 828cc twin won’t suffer too much compared with Kawasaki’s 903cc four. The performance gap only begins to show at high revs. Closing on its 7000rpm redline, the later, lower compression twin produces maybe 50bhp. Big K’s dohc four might be making less torque, and therefore power, at the same speed, but it carries on for another 3000rpm, churning out 82bhp as a result. This adds about 20mph to the maximum speed and ensures that the Z1 will forever be known as a bike with lethal handling. Still, I expect an 80bhp Commando engine in a standard chassis would be at least as wobbly if you tried to use all the power.
The four doesn’t hold all the aces. Subjectively, the rubberised twin is smoother at typical main road cruising speeds. The Kawasaki gets pretty tingly the more it revs, whereas the Norton shows little sign of stress.
That’s why many Commandos fell apart so quickly, of course. Rigidly-mounted parallel twins leave the rider in no doubt that constant high revs will end in disaster: ignorance is not bliss!
All things being equal – which they’re not, as good Z1s sell for far more than good Commandos – I’d probably prefer to have my Norton in the shed than a Kawasaki Z1, but no doubt there would be times when I’d regret it! Sadly, it looks as if I’m going to have neither, because Project Norton must be sold, for financial and space reasons. If you want to buy a nice red Interstate, rebuilt at a cost of several thousand quid, guaranteed to leak oil and break down like a proper classic, get in touch. All sensible offers of wheelbarrows full of tenners considered.*


[End of online sample, you can read the loads of other articles in the September 2003 issue of Classic Bike Guide]

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