Loose Lines: Pie in the Sky [Issue 22, March/April 1990]

I find it a rather sad state of affairs that here we are in 1990 and still so little has been done to improve the design of the modern motorcycle. It’s rather laughable that at the very same time that certain motorcycle magazines jump on the Green bandwagon, they also wet themselves in praise of the latest hyperbike. It has never been clearer that this year’s piece of state of the art will be next years has-been heap of junk, when what we really need (or at least what I need) are long lasting, practical and fun packed motorcycles.
 
The basic requirements for such fun are a machine that weighs in around 375lbs dry and puts out 60 to 70hp at the back wheel. Any lighter and it gets blown all over the road, much heavier and it becomes a pain to sling around town and country roads. Less power will not produce the arm wrenching acceleration necessary for the production of manic grins whilst much more power will start to burn out tyres and chains at an expensive rate.
 
As we are all grown up, sensible hoodlums we'll have to stick with four strokes rather than those two stroke thingies, at least until they master the art of directly injecting the fuel straight into the combustion chamber (which will stop half of it being thrown straight out of the exhaust and radically improve fuel economy). 60-70 horses at the back wheel means around 80hp at the crankshaft which suggests a 750. Yes, sonny, I know it’s possible to knock out those kinds of ponies from a 500 four, these days, but as the engine is supposed to last more than 100000 miles and have as much torque as possible, 750cc is much safer.
 
Twins of such size need huge balance shafts to quell the vibes which in turn eats up all the power. Just to be different, why not use a triple instead of the obligatory four, what little vibes such a layout produces can be adequately quelled with recourse to careful component balancing and, if the worst comes to the worst, a minimal balance shaft. An across the frame triple, these days, can be designed in a much more compact form than older versions such as the Trident and XS750.
 
Water-cooled with five valves per cylinder (bucket and shims, checked every 25000 miles), such a unit could be fed by a self-adjusting fuel injection unit that was part of an electronic management system - OK, it’s complex and has lots of horrible black boxes but it’s the only way to achieve reasonable economy and loadsa torque. Naturally, as this is the last decade of this century it will have gear driven DOHCs on one end of the crank, where it’s easy enough to machine the gear bosses rather than use a separate carrier as per poor old Honda (I forgot to mention that the upper crankcase and cylinder are one piece as per automotive practice). In fact, the only chain on the whole bike will be the final drive.
 
A nice little twist in the design would be use of a separate sump for the engine: the primary drive on the end of the crank and the gearbox thus being free to use oil of adequate thickness. The engine oil, not having to churn around gearbox swarf, will also be able to last much, much longer could 10000 miles be possible between oil changes? Probably.
 
There is little doubt that the above is but a moment's pain for any of the big four to produce, though this is only the starting point. The compact engine, with the cylinders angled forward as per CBR or FZR fours, would form an integral part of an alloy frame whose form would be radically simplified by attaching the swinging arm directly to the back of the engine. However, monoshock suspension would be thrown away in favour of conventional and high quality twin shocks in the traditional position. The alloy swinging arm mounted on sealed, pre-greased bearings, with eccentric adjusters for ease of chain maintenance, ought to be maintenance free for 100000 miles!
 
Retention of chain final drive will be seen in many quarters as an act of heresy, but why not? The modern O-ring chain fitted to a tiny engine sprocket, subjected to huge movements due to ill positioned swinging arms and immersed in road grit, lasts a remarkably long time. One running on a large gearbox sprocket (and I mean large), with a swinging arm mounted close by and the chain enclosed by plastic, should last a wonderfully long time - and a chain in good condition is much more efficient than the twists and turns taken by a shaft drive.
 
The forks would be conventional tele’s, but like the rear units, fitted with gaiters and made to a high standard. Adjustment at both ends would be limited to spring preload decent suspension works without lots of pissing about. Wheels would be wide, probably 17 inchers, and the rubber, thanks to the low mass of the bike and large contact patch of the tyre, long lasting (which means at least 20000 miles) - if this sacrifices ultimate grip, then that is just too bad. The back brake will certainly be a drum, whether or not technology has reached the stage where the front could also be in the same form, I’ve no idea, although the combination of a fork brace and single disc will probably suffice.
 
The need for fuel economy means aerodynamics will play an important role in the styling of the bike, but not the toytown notions of the race replica where a low drag factor is only achieved when the rider isn’t seated on the bike! Essentially, a radically sculptured tank that takes the riders knees out of the airstream and very narrow bars (possible thanks to the low mass) shielded by a fairing along the lines of the boxer BMW RS (although rather slimmer), would combine to give some real life aerodynamic possibilities. It will be a hard task to combine practicality with style, but not an impossible one.
 
Naturally, wherever possible plastic, alloy or stainless steel would be used in favour of plain steel, a huge petrol tank and some storage provision would be provided, and everything would be well tucked in so that if the machine did fall over, damage would be minimal.
 
Power deliver would be decidedly soft below 5000rpm, allowing the rider to potter around when he felt like it and I see no reason why it shouldn’t achieve 100mpg in such a mode if cars can do 60mpg. Radical power would start to flow in beyond that, the bike really coming on cam with a typical triple wail, topping out at 12500rpm. Torque would be such that only four gears would be needed, although it might even be possible to get away with just three!
 
Obviously, at high speeds, fuel economy would degenerate but I see no reason why, with the aid of some decent aerodynamics and efficient engine, sub 100mph speeds should return better than 75mpg (and if you think that unlikely, I used to cruise a ‘66 CB450 at 90mph and get 70mpg). Those same aerodynamics should also make for a top speed of around 145mph and the ability to cruise at a very comfortable 125mph without having arms torn out of sockets or head shook, rattled and rolled by an immoderate wind blast. Handling, braking and ease of use go without saying as even the Japs have these items well sussed now.
 
OK, the important question, what it'll cost. Two points first, a triple is cheaper to make than a four and the overall bike would be so much better than anything else that it would sell by the boat load, in turn lowering unit production costs, in turn selling more - what a happy vicious circle! I certainly see no reason why such a machine should cost more than four grand (although knowing the greed of some importers they would rather not take the risk and sell far fewer at a much a greater profit - shitheads).
 
Neither am I convinced that production of such a good bike would mean the Japs would eventually run out of customers - they would just have to make it better still! And there are, of course, vast numbers of people totally pissed off with the throwaway, ill-conceived modern motorcycle that, for all its speed and handling finesse, requires a huge input of money to keep it on the road after paying out a not insubstantial sum in the first place.
 
Going green has a lot more to it than using unleaded petrol (an act not wholly beneficial in my experience, anyway), it’s just a pity the clowns in the colour comics don’t wake up to what is possible - but then, judging by the awfulness of modern road tests, ignorance has always been bliss in certain quarters.
 
Bill Fowler