Yamaha Rd Aoo
YAMAHA RD AOO
CYCLE WORLD TEST
The Last Pocket Rocket Gets Older and Better
Breeding always tells, we are always told and sure enough, just as the Yamaha RD400 is the last of the two-stroke giant killers, the sole surviving pocket rocket, so does the RD400 come from a long line of champions. Not only that, the RD400 is getting better.
Best of all, the RD400 is getting older.
Nor is the catch phrase turned inside out. What we have in the RD400E, is a delightful machine, a quick little roadster that’ll blow the bars off bikes with twice the displacement and twice the cylinders. We also have a case of the fittest surviving.
Once there were many such bikes. Small, light and usually powered by tw'ostroke engines, the little road burners provided entertainment for those to whom large motors were wasteful and multi cylinders superfluous. The aim was to go fast and efficiently.
The RD400’s direct ancestor was the RD350 of 1973, itself a mix of the earlier R5D engine, plus reed valves and a 6speed transmission, tucked into a doublecradle frame based on the TD racing bikes.
The RD350 became an instant cult. There were other quick little two-strokes about, but those were known in general as flexible flyers, because their engines were more than their frames (and sometimes their riders) could handle. The RD350 was perfect for the sporting types who liked to whiz ’round turns on their ears, in control, and the RD350 won countless production races, in the process drubbing machines up to 750cc.
The 350 was something of a demanding engine, so in 1976 Yamaha introduced the RD400, a larger engine thanks to a longer stroke, with tuning revised to have a bit more power spread across a wader rev range.
The RD400 also got cast alloy wheels and disc brakes and a few styling touches to keep the thing up to date. Most important for the sporting rider, the rubberinsulated engine was moved forward 20mm, for improved weight distribution that kept the front wheel on the ground under power.
The 1978 version of the RD400. called the 400E by the factory, isn’t much changed. No call. The w heels and some of the other cast bits are painted black, the bike has self-canceling turn signals, the
rear fender is topped by a neat duck tail and a taillight that’s now displayed by all the road Yamahas (cheers from owners and parts men) and the stripes and decals get moved hither and yon. The silver paint looks just right; small, sharp and sporting.
In the catalog of last month, Yamaha said it well: Here’s our complete line of road-only two-strokes, the RD400E.
That deserves some comment. The RD400 is a survivor but not a relic. The RD remains while the other sporting twostroke Twins and Triples have gone aw'ay because the RD was the best and is the only member of its class which is still in popular favor.
Mark that. The cheap way out is to throw a few' rocks at the government and the environmentalists, to the tune that they and their new regulations forced the cornpoppers off the market.
The feds and the self-righteous have a lot to answer for, but not this one. The regulations may have made it harder for two-strokes than for four-strokes but they don’t ban any type of engine. If Yamaha could do it for the 400, so could the others have done it for their roadsters. If the government and clean-air lobby had in fact forced popular bikes from the market, why. there w'ould have been a rush on the showTOom unequaled since Indian Territory was given away from the Indians. There was no rush. Instead, as the twostroke market faded away Suzuki and Ka-
wasaki came out with attractive new' fourstrokes and have thereby increased their sales.
We have nobody to blame. Rather, we have this one good, small, fast, sporting two-stroke.
While Yamaha was doing its own complete line of street four-strokes, the RD400 was not being neglected. The usual process of aging has actually been avoided. While the normal thing is for a model to get bigger and slower and festooned with extras. the RD. well, remember that bit about getting better? Look here:
RD350 RD400C RD400E
Weight 344 lb 367 lb 375 lb ‘/4-mi., sec. 14.30 14.14 14.12 ‘/4-mi., speed 89 mph 89 mph 90 mph Top Speed 99 mph 95 mph 99 mph MPG 40 45 44
Pretty nice, eh? The two-strokes still rule racing, with Yamaha the clear ruler, and the best equipped to refine two-stroke design.
Power isn’t the problem. The RD400 is basic even for a two-stroke, with coil and points ignition, two carbs and two reed valves and some careful work with relief valves in the cylinders and with the windows in the pistons, all aimed at curbing some of the snap, crackle and ringy-dingy which (in other bikes) led to the line about how if God intended us to ride tw'o-strokes, we’d be born with cotton in our ears.
One-liners aside, the RD has been made fairly quiet, under most conditions. The massive airbox muffles the intake roar, the two large exhaust pipes bring the exhaust down to legal limits.
The anti-vibration campaign has been an unqualified success. The two-stroke Twin begins w ith an advantage in that the entire operation is close to being one constant power flow, so the great throbbing of the other kind of engine is replaced by a buzz.
Buzzing is nothing. The RD engine is mounted in rubber. Just about the only actual connections between engine/trans and frame would be the exhaust pipes, so the front pipes are mounted firmly to the engine and the aft sections with mufflers are bolted to the frame. Between the two pairs are little accordion-pleat joints, of rubber. The handlebars are insulated with rubber biscuits and so are the pegs. It works. At most speeds, that is, all but a few critical resonances, the rider gets a faint hum and that’s all.
Almost forgot wflat Yamaha left off on purpose. Electric starting. Wise decision.
As with the SR500. the buyers of the RD400 will not be newcomers. They'll be riders with formed, .definite tastes and they’ll welcome not having to buy what they don’t need to use. The kickstarter is all there is. (Unlike the SR500, by the way, the RD can be kicked into action by anybody, with ease, although the choke won’t keep the RD running without hand-supplied throttle during the first minute of cold-morning operation.)
Surprise note here is how far the rationalization of parts has come. Motorcycles built after January 1. 1978 will have their headlights on when the engine is running. But all the ’78 Yamahas we've tried to date have had an on-off switch for the headlight. On a couple of the bikes, the switches worked, on a couple they didn’t. The test RD had a switch that didn’t. It also had the all-Yamaha casting for the right-hand controls with a blank surface where the starter button w'ould have been if there had been one.
The RD400 is in many ways a demanding machine. The pocket rocket fancier will find this no drawback. As the figures show, the RD is quicker than all other recent 400s and most of the 500s and a couple of giants we’ve tested during the previous year or so.
Great bike for the drags. On our best run (backed up within fractions) the RD’s Yokohama Road Speeds bit right oil'the line and the front wheel carried all the way through first and second. Not as scary as it sounds. The 400 has more weight in front than the 350 did and that means that wheelies are an option. The earlier rockets sometimes supplied more rear-wheel riding than the rider demanded.
More care is required for street riding. The tachometer could usefully be divided into segments, like those pie charts showing where the government spends its money. The transition from weak stumble, below 4000 rpm; to useful power. 4-6500; and to Jato Bottle. 65-8500. is that obvious.
The ratio spread within the gearbox is close, especially for the three upper speeds. And the shifter in our test bike had a short throw and a somewhat vague feeling. that is, one pushes or pulls and the lever moves up or down, but doesn’t have a notch or detent or any definite sign that the gearbox has gone from one position into another.
There’s more than enough low end power to get ofi' the mark and through traffic, but a smooth passage to cruising speed requires taking the engine to at least 5 thou in each gear, so it won’t fall off the powerband. When the rider stops shifting up depends upon the legal speed permitted. Because of the peaky engine, cruising at less than 4000 rpm brings surge, bang and rattle and makes city riding a bother unless the engine is keep up to speed.
On the open road, the gearing is better, because cruising at a true 58 mph the average speed on American highways, by actual survey—keeps the 400 at a useful 5 thou.
Unless the rider wishes to speed up or pass a slower vehicle. Then, because the engine is just barely at work and because fourth, fifth and sixth are so close, the RD won't gain speed as desired unless given a double downshift.
All the above is acceptable, mostly because there is no other way. The six speeds provide instant power and practical cruising. Tuning an engine to be the quickest in class brings with it a stage of tune that must be catered to. Cyclists who don’t enjoy dancing up and down the shift pattern are advised to consider buying a mildly-stressed 400 four-stroke. Lord knows there are plenty of them on the market.
Brakes are beyond reproach. The equipment is there and because the RD400 is so compact and well balanced, the brakes can be used to maximum. A skilled rider can even do brakies. i.e. stand the machine on its front wheel, simply by precisely applying the right amount of front brake force.
Speaking of balance, the RD is also good for some trials tricks. Like coming to a stop in traffic without putting down a foot. One of our guys has been doing that in hopes of being able to keep balanced until the light changes, at which time he’ll motor away, leaving (he hopes) a crowd of spectators who don't believe their eyes.
Balance is responsible for some other benefits. Unlike the average small roadster, the RD doesn’t bounce off the wakes of trucks or get carried away by gusty winds> in the mountains. At speed the RD tracks like an arrow.
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Some attention is needed, not because the RD doesn't handle well hut because it is small and powerful. Sudden motions. especially from a heavy rider. vi1l move the RD around. An XS 11 wouldn't even notice.
At 100 percent cornering force the RD vi11 ground the pegs. the center~tand and the exhaust pipes. on both sides. The forks and springs/shocks hint at cost effective ness. The RD will track well at sporting speeds. Pushed beyond that, at 100 percent speed for a given corner, the RD will begin
to shrug and work around. Ride was pleas ant. although we felt that the spring rates were a bit high and the damping. es peciallv on rebound, not high enough. The forks seemed mushy at first impression. \\e changed the factory's fluid to = 10 fork oil. Fork action seemed more positive. although we expect 20 oil would he a better choice.
Considering the size of the RD. riding comfort and the controls are well above average. \len of average height tIt vell. with just a sporting lean forward. The pegs might he an inch or o behind their stock location. as the forward lean puts ones back into a bend. The RD isn’t large enough for two people unless they really want to go for a ride. The seat itself is flatter and more square than we remember from the 400C. The 400E is also more comfortable than expected. The seat is softer than it looks and the pegs are high enough so that most of the crew sat so their legs didn’t rest on the edge of the cushion.
Miles-per-gallon varied widely. The staff light-finger got 48 mpg and the boy racers got as low as 39 mpg. The normal test turned 44 mpg. As they say in the disclaimers, the results you get may vary, depending on your riding habits.
Speaking of that, the bike you buy also varies with your riding habits. The RD400E is a roadster, quick and demanding. It will commute, provided the rider is prepared to put up w ith paying attention at all times, and will tolerate not using the RD’s sporting potential except on those rare and joyful occasions when the road needs to be ridden.
Relief that the RD is getting older stems from Yamaha’s announcement that the model will be in the line-up at least until 1980.
Good, ’cause for those of us who want a
pocket rocket, the RD400 is it.
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YAMAHA
RDOOOE
$1289
Although the spring rate is adequate, rebound damping rate and seal friction are not. Use 20 wt. oil to increase damping; this will result in a firmer ride, but will improve control. Swap the stock seals for some aftermarket units if a slight improvement in fork compliance is desired.
Rebound damping of the stock shocks is totally inadequate, and allows the bike’s rear to wallow when pushed hard in corners. A set of aftermarket shocks would be a worthwhile modification; the stock spring rate should be maintained, as it is appropriate.
Tests performed at Number 1 Products
