YAMAHA RD400
Jon Bentman rides Niall Mackenzie’s lovely Yam.
Yamaha’s RD400 was born into a confusing world where customers wanted more performance, but legislators wanted less emissions, where simplicity was key and yet complexity sold. It was then something of a mixed-up contrivance. Yet it succeeded, handsomely.
Our headline explains all about the RD400: so much of it is wrong, but success is carried off because in the end the balance is just about tipped in favour of the right.
And by heck is there a confusion of influences around this model, from beginning to end. It is to its credit that it can shirk all its failings and shortcomings and appear as the pristine example of a true motorcycling icon.
Let’s start with its predecessor the RD350. First made metal in 1973, that bike emerged as part of a newly united Yamaha family. Up until 1973 the series of Yamaha two-strokes was muddled. The RD350’S immediate predecessor had been named the R5, while it’s sibling 250 was named the (Y) DS7. Meanwhile, a 200 was named the CS5 and a 125 the AS3. Dare we mention the production racers, which in fact bore a lot of shared components c with the roadsters? Here we had the 350cc TR3 (based on the R5 road bike), the 250cc TD2B (based on the YDS6, updated). It was a mess of nomenclature, and someone, somewhere in the Yamaha management must have cried ‘Enough’. So, in 1973 the Yamaha two-stroke road bikes were at last renamed collectively the RD series (RD – Race Developed) and the racers TZ (why TZ? Answers on a postcard…)
Now while the RD350 was ‘race developed’, we should note that RDS are a long way short of
being road-going TZS. Back in 1973, when the RD350 could barely top 106mph, the new TZ350 was good (on paper) for 156mph. So while some parts were shared (in general design at least – and let’s not start on the water-cooling), the difference was sufficient for the American market to consider the RD a touring motorcycle. That said, the RD350 was lairy in its own way. Despite the calming influence of reed-valves (newly introduced for this model) the RD still came into its powerband with a bang; combined with a taut chassis and that defined top-end it was a lively performer.
So, in 1976, the RD400: why 400cc? While racing was sticking with the 250/350/500 cubic capacities, the manufacturers were experimenting with differing cubic capacities for the road bikes. Kawasaki had enlarged their S2 350 into a KH400. Suzuki’s T350 twin had given way to a GT380 triple, and Honda had just launched the CB400/4. Four-hundreds had become plat du jour.
Only the RD400 wasn’t just an over-bored RD350. Many things happened. For a start it isn’t a bored 350, instead a long-stroked version, with an added 8mm (so it could retain the same crankcases – a nice cost saving). And while the frame retained the same geometry as the RD350, the engine was budged forward by 20mm, bringing more weight on to the occasionally wayward front wheel and the engine was now rubber mounted.
And it wasn’t just the engine. Count in the handlebars, fuel tank, a rubber gasket between the header pipes and mufflers, and then the rubber mounted footrests on brackets that hooked out from underneath the exhausts.
Let’s add a big squishy seat and take note of the high handlebars and forward placement of the foot-pegs. All of this suggests creature comforts for the touring rider. Equally, that capacity increase had come not to heighten the top-end performance – which remained unchanged (top speed, RD350: 106mph, RD400: 106mph) – but to plump and smooth the bottom-to-mid range.
The softening doesn’t end there. The suspension was decidedly comfortable, not sporty (it would be firmed up in 1978, with the E-model). Ah yes, and the rubber-mounted engine was thought to allow the frame to flex more than the rigidly mounted RD350 motor had allowed. Everything points to improved civility. The angular styling (coffin-tank and all) was considered European in taste, and yet the bike appears to be Us-biased in dynamic.
And that engine. Beautifully simplistic as it is, a master class in economy (of parts), it was not tuned for performance. Today we’re inclined to recall tales of wheelies and hectic back road scratching when talking of RDS. But the stats suggest otherwise. While Yamaha claimed 40hp for the RD, it didn’t produce this. Typically it was tested at around 34-35hp (same as the RD350) and this compares directly with the likes of the 400/4, which made a claimed 37hp and even – God forbid – the later 400T (twin), which produced just shy of 36hp.
And should we discuss weight: brochure weight, RD400 – 166kg. Honda 400/4 wet 185kg – dry, less 14 litres of fuel, say 171kg. Now the RD400’S engine was just two kilos heavier than the 155-kilo RD350’S, so it was in the chassis that Yamaha let
“The RD400’S character changes as the revs come up. Approaching 6000rpm the RD comes on pipe in a determined manner. It pulls strong, and with a distinct mid-range hit.”
the pounds (or kilos) pack on. Much of it is probably in the cast wheels. These were the first ever seen on a production bike (albeit an option in 1976, standard from 1977) and probably over-engineered as a consequence. Later, from 1978, they were made lighter, but these were still boat anchor heavy; it’s a miracle the RD still steered as sharp as it did. Considered quick steering for the day, with sharp brakes too (maybe too sharp at the rear), it could
– for a ‘tourer’ – seriously hustle.
The RD400 was thought on paper and in the real world not much better performing than the new four-stroke 400s, when it should have been miles better – much lighter and much faster (a failure that would be corrected to startling effect by the RD350LC). However, that didn’t matter because it still held two aces. It was cheap. And it was simple.
The Honda 400/4 was a poor man’s CB750, but still a rich man’s toy at £818. The RD400 was a more attainable £675 (or £599, depending on source material). And when it came to maintenance, the Honda had that camshaft, those valves, those four carburetors to keep in synch. The RD was simple to maintain and it could be tuned (quite easily) to go much faster.
So the RD400 would dominate on track, where proddie racers were bending the pipes up-and-in to get cornering clearance – but still cursing those foot-pegs – and on the street, where ‘cheap and fast’ always sells.
Two-strokes were, however, losing market appeal in the US, where big power would always win over cornering agility, and where in any case big capacity was taking over as the Japanese got the hang of 750cc+ four-stroke multis.
In Europe, where no road runs straight for very long, good nimble handling machines still won out. And as the competition waned, leaving just the RD400 easily beating the aesthetically turgid CB400T and even more forgettable twins from Suzuki and Kawasaki, the RD lived long and prospered despite all its shortcomings.
The RD400 was, then, able to keep the two-stroke flame alive, if only to light the blue touch paper to the rocket that would be the LC, and the high performance two-stroke street racers that would follow.
THE RIDE
This was a last hurrah for the 1970s. The RD400 held sway in the middle ground of the middleweights, but its days were numbered; come June 1980 the RD350LC would kill it stone dead.
But in 1979 this was the moto-date every young motorcycle-mad Brit male hankered for. Those Yamaha US colours, the yellow/black/white speed block, spoke of TZ on-track superiority. And around the converted WWII airfields that were the mainstay of the UK’S racing scene, the RD400 was as dominant in the proddie classes as King Kenny was in the somewhat more glamorous GPS.
You can tell all this when you fire it up, sort of. Its successor, the LC, burbles on tick over, but this RD has a slightly meaner edge. Being air-cooled, not cloaked in a water-jacket you just hear it, feel it more. Rev it and the RD gets louder, the baffles rattle and the cylinder fins vibrate, almost making the air shake. Throw in the blue haze of unburned hydrocarbons, and you know activities of a nefarious nature are afoot.
The ergonomics come from an earlier time. The handlebars almost sit in your lap, while your feet rest on foot-pegs that are high and forward, almost like an old Brit bike. And while the RD may sou und a good deal racier
than the plodding
350cc Norton, Brit Bike Man will actually find the RD400 to be quite amenable in the lower revs. Often two-strokes get characterised as high-revving, razoredged devices, and while that might be true of older road racers, so many two-stroke road bikes are in fact far more flexible and easier to ride than even mid-sized four-strokes. Of course that all changes as the revs come up, and approaching 6000rpm the RD comes on pipe in a fairly determined manner. It pulls strong, there’s a distinct mid-range hit – but those reed-valves that debuted with the RD range (in 1973) make for a broad controllable hit of power. The feeling from the engine is similar between the RD and later LC. You can feel that typical Yamaha flexibility, they have a certain character, but the LC with that water-jacket and a little more refinement is the smoother, more potent of the two.
The handling is pretty smart on the RD. Ridden in the company of the LC (with a svelte Niall Mackenzie in the LC’S saddle) the RD keeps up nicely, has good straightline stability, at legal road speeds it doesn’t wobble or weave, and it tips into a corner with ease and generally – if not exactly – keeps to a line. And given it has even less braking than the LC (just the one front disc, albeit supported by a sizeable rear disc – Yamaha went back to a drum on the LC) you inadvertently make up ground into the corners… Riding on the road it gives little away to the LC, but as Niall explained, on track the superior ground clearance, more than anything, meant the LC would run rings around the RD.
In all, the RD is a fine ride. This RD400F is the culmination of six years as a listed model – plus the years in development. It’s fully debugged and is a pleasure to ride. It does nothing wrong and, in fact, is a quick set of wheels. With a near 110mph top speed (easily improved with a little tuning) and being light on its feet despite the fair 170-kilo weight, you can see how it hassled the litre bikes on street and track back in the 1970s.
Yet in a modern context the RD feels surprisingly compliant. Despite its competition successes it was in truth something of a softer ride than it’s predecessor: softer seat, softer handling and – with all the rubber mounting – softer for the rider. All of which make it an any-ride bike, from corner shop dash through to continental tour, it’ll do it all. And yes, you can mix in a little track abuse somewhere along the way. But somehow, especially given the teenage hooligan references often dressed around the RD400, the lasting memory is of the civility! How unusual.
BUYING & OWNING
Let’s start at the top: £6000. That’s pretty full, mind – cash is king in this faltering economy and there’s probably wiggle room there for something with a five at the front-end. And, of course, that’s reserved for a top example: matching numbers, either beautifully/faithfully restored or an immaculate original. And that’s a grand to a grand-and-a-half less than a top LC – which tells you something of the difference in popularity of the two at this time. Likewise at the bottom end of the market, a push-into-your-van (parts missing, but enough there to stir some optimism) complete restoration case can be found for around £1500, again about a grand less than an equivalent LC project.
A quick word here. Five years ago the top price for an RD400 was about £4000. Like all classics, their prices have been boosted by the failing economy and poor returns on cash and other investments in the UK. That’s a growth rate of around 8.5% a year, to create a 50% growth in value over the five years. Be interesting to see if this level of growth in classic values continues.
So far, so good. The beauty of the RD is its simplicity and that holds for everything from the ignition switch, to the engine tech, to the suspension components. It was never said, but was quite probably in the planning, that these bikes were designed with the clueless teenage rider in mind. No specialist knowledge or tools needed. So if things are a little tired, worn out or just broke, then replacement is pretty straightforward.
Engine-wise, it doesn’t come any more simple than the RD. Piston-port barrels, with no water-cooling, just a reed-valve in the inlet. Release the eight head bolts, lift head and the two copper gaskets off, lift barrels off, remove circlip from gudgeon pin, remove pistons. It is that simple and cheap. Replacement piston kits from a reputable manufacturer (Mitaka) say £50 each. Head
gasket £20. Inlet rubbers £20: a beer money bike!
Likewise if you need some help with the reconditioning – bores/honing: it comes at very easy rates because these are straightforward jobs. And when it comes to issues like crank rebuilds, again the simplicity of the motor helps, the labyrinth seal should mean you don’t need to split the crank while quality replacement bearings from the like of Koyo all come at basement prices. Even if the shocks are clapped out, replacement units can be had from £50 (the pair.) Likewise, quality replica chromed steel mudguards can be found for £125 a pair.
It’s not all cheap. Things that rot, or get easily accident damaged, will cost. So watch out for pristine headlamps, for instance. Standard exhausts are, of course, going to be an expense: so many got mangled during the proddie-racing years that supply today is limited. You can try doing something like grabbing some slightly beaten-up mufflers (say £75) and between welding, polishing and replating you can probably come up with something good. We found a rare pair of NOS mufflers on fleabay – asking price £490 each! Or go for a set of periodcorrect spannies (Allspeeds £600).
Beware that while the RD400 ran from 1976 to 79 (four years), the 78/79 models saw quite a few differences to the earlier ones. For a start they got CDI ignition. Then you can add revised cylinder porting, different pistons, exhausts even carburetors, hinged frame-mounted footrests – and the brakes, too, changed from opposed twin-piston calipers to single piston floating type. However, that doesn’t stop the parts being interchangeable.
And that also goes for parts from the RD250S which ran alongside the RD400S – so many parts from that model are interchangeable. Look out for the model codes to know what you’re handling, RD400S chassis and engines are stamped with the prefix 1A1 and 1A3 (early/late), while RD250S are 1A2 and 1A4, but like all things it’s never that simple, there are other product codes too – so check in with the likes of aircooledrdclub.com to get a full rundown of all relevant codes/numbers.
CONCLUSION
Unquestionably, the RD400 has been eclipsed by the LC. Obviously, from 1976-1979 it wasn’t, and back then it ruled the roost, but once the LC arrived the 400 was regarded as yesterday’s news. And even in the context of modern classics today, while we’re falling over ourselves to pour compliments on the LC, the RD400 – while not forgotten – certainly gets second billing.
It is nonetheless a true classic, helped by having been so dominant for half a decade, but also by being today an all-round nice ride. Easy to live with, to work on, while being comfortable and a little sporty when it comes to the riding. Heavier than it needed to be, slower than it could have been, yet somehow still a gem of a middleweight.