The magazine for classic Japanese motorcycles

80s from the eighties

As anyone who wandered around last October’s Stafford Show will have realised, the classic motorcycling scene isn’t just about big, or even mid-sized bikes. There’s a growing fan base who are inspired by and look after lightweights from the 70s and 80s, and it’s not confined to those who try to relive their pubescent Fizzie days.

Trouble is a lot of the small bikes from that era have long since been worn out and scrapped, and that’s hardly a surprise. Many were dull and uninspiring, and just a means of transport that was slightly more appealing than either walking the five miles to work or being crammed in a bus. Occasionally they’d escape the tip, and there are those among us who feel they have a responsibility to restore them so that their place in history is properly recognised. The Honda Chappy is a prime example.

Insurance companies can share some of the blame for the ranges of often miserable bikes that were on offer. Novice riders were encouraged to buy racy-looking 125s while confined to L-plates, so it was inevitable that this was a category regarded by the insurance firms as being most risky, and hiked the premiums accordingly. Avoidance of this was possible by riders opting for a 100cc machine, which attracted a less costly premium.

This choice however risked mockery from your mates, because these smaller bikes were less flashy even though they were only slightly-less potent. In describing these bikes as less flashy I’m being generous: they were basic in the extreme such as Yamaha’s RS100 two-stroke single, an understated offering that might have been regarded as the height of luxury on the streets in the Philippines but the mark of a social outcast in Portsmouth. The manufacturers – Honda, Kawasaki, Suzuki and Yamaha – seemed happy with this arrangement because they could offload the cut price Asian-market runabouts in the UK and still make a good margin with a price tag of less than £500.

Elsewhere in Europe there were more enlightened legislators who allowed manufacturers to offer more sporty 80cc machines. Some were hopped-up fifties, with the result that riders could have about as much fun without breaking the bank. Both Kawasaki and Yamaha saw this as an opportunity to enliven the 100cc class in the UK so for the 1982 model year included the AR80 and RD80LC in their ranges alongside the commuter bikes, among which they sparkled like the miniaturized racers they were.

With 10 horsepower available both bikes could top 60mph, or twice that of the restricted 50cc machines. Now you might scoff at such a meagre velocity, but it was not far short of what the restricted 125cc bikes could manage and in the urban environment this was of little consequence. What mattered more was their style and the handling. Scaled down versions of the bigger sports bikes, they weighed less than 100 kilograms, could turn on a sixpence and wheelie at the flick of the wrist. Neither was short of technical interest however.

Kawasaki’s AR80 was closely based on the AR50, which being designed for meeting various regulations that restricted its top speed for novice riders, was horribly slow. But the styling of both gave the impression of being much faster. The sleek angular fuel tank and matching side panels enabled the rider to tuck in behind the signature Kawasaki nacelle – almost like the GPz1100’s – and plot the next overtaking move. The clip-on grips provided a direct connection to precise steering which with so little weight to control provided millimetric accuracy in the ducking and diving between the traffic.

I was a bit over-zealous in my description of the AR80’s chassis when I tested the bike for Which Bike? in the spring of 1982, suggesting that the reason why it felt like a racer was because it was built like one. Weight-wise, perhaps yes, because Kawasaki claimed a dry weight of 172 pounds (78kg) and even with a full 10-litre tank it tipped the scales at just 205 pounds (93kg). And certainly there was trickery in the suspension, which made up for the simple semi-duplex loop frame in fabricated steel tubing, giving a wheelbase of 47.4 inches (1205mm), a full 10 inches less than the average superbike.

Up front, the longish-travel telescopic fork featured leading-axle sliders (again, just like the bigger Kwaks) while the Uni-trak rear – similar to that used on Kork Ballington’s world-championship winning 250cc racers – was best-practice, the triangulated swingarm connected by a rocker-arm linkage to a vertically-mounted shock with preload adjustment making the accommodation of a passenger a practical proposition.

All this was allied to gold-finished 18-inch five-spoke cast-alloy wheels, a potent 210mm front disc brake and a level of detailing and grown-up instrumentation that would have shamed much more expensive bikes than the AR80, which was listed at £499. Even the expansion chamber-style exhaust system was a miniature work of art. No wonder fans of the bike restore them for display in their homes. You’d think that with so little weight, the ride quality would be no better than a bicycle’s, but the AR80’s long-travel suspension soaked up the surface like a motocrosser.

The bike felt pliant and grippy enough to inspire antics that were as much fun as on any sport bike, but without the attendant high-speed risks. Every red traffic light was an invitation to perform a stoppie in the best of hooligan behaviour. Oh yes, I confess to a mis-spent past. The outright performance data I obtained at MIRA’s test strip does the AR80 scant justice in relating the delight that could be had in picking lines through town traffic or twisty lanes. At MIRA the little Kawasaki almost reached its top speed of 60.4mph within the quarter-mile acceleration tests, so every trip on A-roads away from the urban bustle was like a mini TT race, the bike held with the grip wide-open with momentum maintained for as long as possible before the need to brake for corners became necessary.

The AR80 was at its best where the roads limited you to 50mph where the engine’s power – not much of it but with a feisty delivery – could be used to the best effect. Based on the AR50’s 49cc air-cooled unit, the AR80’s engine featured a bigger 49mm bore which with the same 41.6mm crankshaft gave 78cc. Breathing through a reed inlet valve and an 18mm-bore Mikuni carburettor, the engine peaked at a claimed 10bhp at 8000rpm though according to the rev meter it seemed like most of the power was above this.

It never baulked at being wrung to 10,000 and indeed seemed to revel in the treatment, apart from transmitting a few resonant vibes through the footrests and handlebars. In fact the engine was surprisingly flexible, and even though when used hard returned a consumption of slightly more than 74mpg, enough for a tank range of more than 140 miles. Overall gearing through the six-speed box felt low and this was shown in the performance figures. Sitting normally on the bike, I clocked 56.3mph, which was only four mph down on the flat-on-the-tank figure, suggesting that the power tailed off on reaching 9000rpm. Average acceleration time through the quarter mile was 21.3 seconds with a terminal speed of 55.5mph, and although sounding snail like was not far short of the 19.36s/64.0mph I recorded for a 12bhp RD125LC a year later (though of course an unrestricted 20bhp version would be in a different league).

The Kawasaki was the style icon of the pair, but the Yamaha RD80LC made the AR80’s technical features look tame by comparison. An altogether upmarket machine, the RD80LC looked more derived from the bigger 125LC than a 50, and this was reflected in the higher price of £625. In fact, the Yamaha was based on a 50cc machine sold in Japan, but with a number of refinements that included liquid-cooling and a vibration-absorbing system.

A bigger machine with a longer 48.4-inch (1210mm) wheelbase, the Yamaha featured all that had made the LC models so stylish but in more compact package: an angular tank, chiselled belly pan, matching radiator cover and Monoshock suspension with a triangulated swingarm and horizontal shock under the seat. With its liquid-cooling jacket, the engine was so small it was dwarfed by the ancillaries such as the oil-pump casing and capacitor-discharge ignition cover.

Inside, the 79cc capacity resulted from a 49mm bore and 42mm stroke and the tighter clearances used with the liquid-cooling made a lower 7.1 to 1 compression ratio possible, compared with the Kawasaki’s 7.8 to 1 figure, both of which were measured from the closure of the exhaust port, rather than the ratio of the volume swept by the piston in relation to the trapped volume at top dead centre. A novel feature was the YEIS chamber, connected to the reed-valve body between the 18mm Mikuni carburettor and the cylinder, and devised to resonate at particular revs to boost the mid-range power.

Another clever feature was the engine mount design. At the front of the motor, two rubber mounts absorbed vibration from the crankshaft. This movement was allowed at the rear of the engine by a pair of supports with needle-roller bearings just above the swingarm pivot. So the buzz is absorbed without losing the drive sprocket’s alignment with the rear wheel or chain tension, making the RD80LC much more refined and comfortable to ride than the AR80.

Like the Kawasaki, claimed peak power from the Yamaha was 10bhp but at slightly higher revs, 8500rpm. Gearing through the similar six-speed gearbox was lower in the first three ratios, giving the Yamaha the edge in town where it was quicker off the mark despite the tanked-up weight being 11 pounds higher at 216 pounds. Pulling away from a stop, just snapping the throttle after changing up at 7000rpm lifted the front wheel, and all before reaching 30mph. Joy unbounded.

In top the RD80LC’s peak power revs of 8500rpm equated to 55mph, but it was capable of much more than this, revving easily to the red line at 10,000rpm with the slightest of tail winds showing almost 70mph on the speedo. Performance tested at MIRA at the same time as the Kawasaki, the Yamaha was fastest, clocking a mean 62.2mph flat out. Seated normally the top speed dropped to 57.3mph, suggesting that the gearing was about right. Through the quarter mile, the 80LC proved to be quicker by almost a second, clocking a time of 20.5 seconds with a higher terminal speed of 58.9mph.

From a first glance, you’d think that the Yamaha’s rearward weight bias of the engine would make the front end flighty, and under acceleration it was, but like the Kawasaki’s, the RD80LC’s handling was brilliant. Think the bike to a spot, and there it’d be in an instant, all with surprising stability. Like the bigger LC models of the time, the 80 featured a conventional handlebar but with rear set footrests encouraged a racing stance. Their positioning meant that the right footrest needed to be folded up to allow the kick-start lever to be used.

As on the Kawasaki, prior use of a mixture enrichening button on the carb enabled cold starts with just a stab or two on the lever. Instrumentation on the Yamaha was just as stylish inside the fairing as the Kawasaki, and was augmented by an engine temperature gauge, so the rider could justifiably fantasize that this was a bigger bike, just in slower motion. Looked at practically, the RD80LC was less economic to run than the AR80, returning 70.6mpg but still giving a useful range from the bigger 2.2 gallon tank even when rushed about at the limit of its performance.

But that was what both these bikes were all about. You could use every bit of ounce of the power and handling and were both huge fun so long as you avoided dual carriageways and motorways which were both boring and hairy with most traffic cruising at higher speeds. But was the RD80LC really worth £625 when you could buy a DT125LX trail bike for about the same, the similar DT100 off-roader for less, or an air-cooled DT80MX for much less, though the smaller bikes were nothing like as quick.

In the 1980s, bikes with 80cc engines became popular in many countries where license regs encouraged their use. The world road racing authorities even replaced the tiddler 50cc class with 80cc machines in1983 until it was phased out a few years later. But the class fizzled out here in the UK.

Until recently, that is, when a few of the survivors were revived by RD80LC enthusiasts like Gary Robinson here in the UK who regard them as micro-icons of a bygone age. It was his bike with the dual paint job at Stafford. After building half-a-dozen he’s even started restoring them for others who see nothing bizarre in using them as decoration in their homes. That’s right; these bikes are not for riding. Gary reckons his are too good to be used. His restorations are back to new, and to run them would spoil their purity.