Wednesday, 3 January 2018

Hundred Quid Hacks: Yamaha RD200 and Honda CB200


Back in the seventies, when learners could burn around the streets on 250s, most Jap manufacturers reserved the 200cc category for slightly more sophisticated and sensible bikes. Thus both the Yamaha RD200 and Honda CB200 benefited from relatively mild motors, electric starts and reasonable economy. They tended to be purchased by experienced motorcyclists and to escape the harsh treatment attracted by their slightly larger brothers. With prices wrecked by the 125 laws, they represent bargain buys for cost-conscious purchasers.

The CB200 engine represents the final development of Honda's evolution of the small four stroke twin. It shares the same basic design as those early sixties twins that made Honda‘s reputation as builders of oil tight, reliable and high revving engines. A four bearing crankshaft supports two pistons that move in unison. A single overhead camshaft, driven from the centre of the crankshaft,  operates two valves per cylinder with screw and locknut valve clearance adjustment. Gear primary drive, through a multi-plate clutch, to a five speed box. The engine is only lacking in an excess of balance shafts to cure a non-existent vibration problem.

The RD200 engine is built along similar tough lines to the Honda. It doesn't represent state of the art two stroke technology, but Yamaha's decision to use a mild state of tune to overcome their engine's penchant for burning holes in pistons means that the RD can almost equal the Honda's reliability. The engine has the pistons moving out of phase, the usual four bearing crankshaft, gear primary drive, multi-plate clutch and five speed gearbox. Reed valves are placed between carbs and induction port, to allow reasonable port size while maintaining some kind of mid-range torque. As two stroke twins go,the RD200 is one of the better engine designs.

When new, Honda claim 18hp and Yamaha 20hp. The effect of 12 years use and over thirty thousand miles on either bike has blurred any distinctive effect such power difference might once have held. Neither bike has been rebored, tuned or given much more than perfunctory maintenance. The Honda needs its 1000 mile oil change and the RD its 750 mile ignition timing check. Otherwise, life is laid back enough to the point of boredom, the quest to blow the engines hindered by their sheer toughness and imperviousness to flat out riding.

The Honda is as happy at 30mph as at 75mph. Top speed is a true 80mph, an indicated 90mph. Flat out, the limits of two pistons moving up and down together with no balance shafts to overcome primary vibration, are felt as graunching vibration through the petrol tank and footrests. Backing off the throttle slightly removes the vibes, reducing top speed to just under a true 80mph. Continual riding in the vibration zone seems to do no harm to the engine. 

The RD has a similar top speed - a little faster in favourable conditions and a little slower up hills or against a strong wind. The engine is always smooth, there's no obvious vibration to warn against straying beyond the redline. The only sign of hard use, the clouds of blue smoke that haunt the trail of the Yamaha. Below 40mph,in top gear, the RD is caught out by a handful of throttle, when the motor stutters before clearing out the engine. It's far more responsive in fourth at low speeds.

The Yamaha can take the Honda from a standing start, the CB needing 40mph on the clock before it starts to catch up with the RD. Either bike can burn off silly young men in Golf GTis in town, but both are in trouble in the motorway fast lane.

The Honda also gets into trouble when there's a combination of high speed and bumpy roads. The main problem, the front forks which despite thicker oil, lacks sufficient damping to adequately control the reasonably taut springing. It never develops into a speed wobble, just lacks precision and can let the bike wander way off line. The geometry of the CB helps high speed stability and makes it difficult to lift the front wheel from a standing start. Standard rear shocks are useless after a couple of years and have been replaced with Girlings, which while not very special or high tech, keep the back end under control. The swinging arm bearings need replacing every 10000 miles.

The RD is rather more precise than the Honda, with much better front forks and a slightly stiffer tubular frame. The Yam suffers a slightly weak swinging arm and bearings that need replacing at the same mileage as the Honda. The Yamaha's geometry is less concerned with stability, concentrating on flickability and high street credibility. A handful of throttle and a slight pull on the bars has the front wheel high in the air. On worn tyres the RD can come close to converting an 80mph weave into a violent speed wobble. The blame lies with that weak swinging arm.

Country roads see the bikes evenly matched. The Honda's superior midrange torque is pitted against the Yam's agile chassis. The Honda is further hindered by a transmission that loses most of its precision after 30000 miles. It was all too easy to miss a gear if the change was hurried. The Yam's gearchange was largely unaffected by ageing, retaining a nice quick action. Neither bike could select neutral from a standstill. It was just as well that the Honda didn't need too many changes to maintain respectable speeds.

Handling problems on the CB finally came to a head on a narrow country lane. The Honda was doing sixty down a steep hill that curved sharply to the right at the bottom. The sudden emergence of a van around this bend meant there was hardly any space to pass. Braking hard, shift down the box and aiming for the left side of the road produced a bike out of gear, twisted forks that didn't absorb the bumps, and a bike that couldn't be directed with any kind of precision. The face of the van driver looked as frightened as I felt. Ramming the bike into the bank of earth along the side of the road was the only sensible thing to do. The van driver must have had the same idea because a small gap emerged. The Honda survived with a large clump of earth attached to the footrest.



To be fair, both these bikes are twelve years old and their low weight helps save them from any real nastiness. But the Yamaha has more feel and is more precise. Wet weather riding was fine, except that both bikes could lock their rear wheels with absurd ease. With SLS drums like that who needs disc brakes on the rear wheel? The Yamaha didn't acquire a disc front brake until '76, but the TLS drum was just as powerful, had brake shoes that last for over 15000 miles and the drum was as effective in the wet as in the dry. The same couldn't be said for the single front disc of the Honda. Wet weather lag was only bettered by the sudden application of brake pads once the water had been cleared off the disc. The disc needs to be dismantled every five thousand miles to avoid seizure of the calipers. The pads last for 7500 miles. It just about equals the power of the RD's drum. The joys of fashion...

The Honda is way ahead of the Yamaha in the fuel economy stakes. The RD isn't too bad for a two stroke, averaging 65mpg, but it must still lose some fuel straight out of the exhaust port. The Honda manages to average 80mpg. This is better than some of the much slower single carb CD versions. Flat out riding increases that figure to 70mpg, whereas the poor old RD is hemorrhaging badly at 45mpg. Timid right wrists will get either bike to return just under 100mpg. The RD has a larger tank with just over two and a half gallons, giving a range of 140 miles before reserve. The Honda has room for just two gallons and a range of 130 miles. The filter in the CB's petrol tank can clog up easily, making reserve useless, which further reduces the range to 110 miles

Neither bike is comfortable for more than a hundred miles. Forward mounted footrests make use of the passenger pegs mandatory for flat out cruising. The Honda has the least comfortable seat, one that retains water and has too soft foam. The CB200 engine is more durable than the Yam. It can keep going to 40000 miles, when it might just get away with a rebore - usually it needs a new camchain and camshaft, while some cylinder heads are so wrecked that a new one needs to be found at the breakers. Lack of regular oil changes are the only thing to ruin the engine in low mileages, when the accumulated engine swarf wrecks the camshaft bearing surfaces, camshafts and pistons.

The crankshaft is so tough that it outlives the rest of the engine. With fifty grand on the clock, the clutch and gearbox cease functioning; using new parts to renovate them will cost more than the original price of the bike. Contact breakers last for ten to twelve thousand miles, although nifty use of a file can extend their life for another few thousand miles.

Most RD200 engines are in trouble by thirty thousand miles, some struggle on to as much as 35000 miles. The roller bearing crankshaft is the most expensive item on the repair list. Supplied with only intermittent oiling in true two stroke fashion, it needs a complete rebuild. The engine will also need a rebore. The gearbox and clutch don't seem much affected by high mileages. Contact breakers need replacing around 7500 miles and spark plugs need changing every three thousand miles to avoid difficult starting. The electric starter is out of action by 40000 miles. Both engines are straightforward to maintain and to strip down. The Yam needs a strobe for the timing, but otherwise they are just as simple as British bikes.

The Honda escapes the camchain tensioner horrors of some other Honda models, while the Yamaha avoids the overheating and over-stressing of some of the other RD models. There are big bore kits (240cc), wilder camshafts, two into one exhausts and improved air filters available for the CB200. Stock silencers can last for four years before they disintegrate into a pile of ferrous oxide. Pattern silencers work quite well , although don't expect the increased. noise to lead to better performance. Two into one systems seem to upset the carbs, as do non-standard air filters. One bike, with 240cc kit, two into one exhaust, open carbs and high lift cams, managed to shift the CB up to a true 90mph, unfortunately, economy was shattered to a mere 45mpg, and vibration was a fair imitation of a BSA B25. The whole balance of the bike had been wrecked. 

The Yamaha isn't all that well supplied with tuning goodies. Most of the performance kit manufacturers concentrated on the 125 and 250 twins. It's possible to find some expansion chambers and perform the usual ministrations to the engine with a file. The usual result of tuning the engine is to lose mid-range power, hole or seize pistons and increase fuel economy to Kawasaki triple levels. The easiest way to make the RD200 go faster is to fit the 250 engine. Silencers last for much longer than the Honda, thanks to a liberal coating of oil applied to their internals by the inefficient two stroke engine process. The Yamaha and Honda engines both benefit from being left as stock as possible. The manufacturers achieved a decent compromise between economy and performance, that is easily lost by the addition of non-standard parts. Decent shocks, forks and tyres are the only sensible additions. 

Tyre wear was similar on both bikes. The Honda came out worst with just 8000 miles from a rear Michelin, but on other tyres it matched the Yamaha's 14000 miles rear and 15000 miles front. The Yamaha and the Honda are similar in concept but different in feel. The RD is more fun on country roads and in town, the Honda more relaxed and stable on long motorway journeys. The sharpness and smoothness of the two stroke are eventually overwhelmed by the durability and efficiency of the four stroke.

Buying from new the Yamaha would probably have won, but in the hundred quid hack stakes the Honda is the better buy, not least because there are still plenty of low mileage bikes with only a few owners available. Still, for just £100 the RD can be such good company. 

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