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On the move: Honda XBR 500 and Yamaha SRX 6

Single cylinder in comparison: Honda XBR 500 and Yamaha SRX 6

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Is less motorcycling more fun? With their powerful single cylinders, the Honda XBR 500 and Yamaha SRX 6 opened a new round of eternal discussion a good 25 years ago.

I.n lively alternating curves, a narrow lane explores the topography of a hilly landscape, alternating between light spring forest and wide open country. Occasionally there are serpentines, but the sun is always shining. Many motorcycle stories begin with heavenly cliches of this kind and thus pretend that every motorcycle is good for heaven. Wrong, because there is no longer any pressure to perform and those seeking recognition are all stuck in a traffic jam in front of the entrance. That’s why this story tries it with two single cylinders.

Down below, too, their sonorous sound is dazzling, especially thrilling in the here and now, as they enable upscale driving fun with simple means. Two wheels, a frame, a single cylinder – the beginnings are close, nobody can ride a motorcycle more originally, and after just a few kilometers the question arises why the single cylinder in the street motorcycle had such an eventful history: While it dominated for many decades up to the quarter liter class, the twin put him under pressure early on with larger displacements. After all: with BSA Gold Star, Horex Regina and Co, he stayed in those higher spheres until the post-war period from which Japanese performance drive drove him from the mid-1960s. Seemingly forever. But the myth of the reliable steam hammer with a lot of punch from idle speed and great sound lived on. In Europe in particular, it proved to be so vital that Yamaha derived a street motorcycle from the Enduro XT 500, the SR 500. Its technical equipment was not enough to move up to the 40 to 50 hp middle class at the time, but its overwhelming success was the driving force behind it the advance into precisely these performance regions. A relief was the fact that the growing enduro scene also demanded strong single cylinders.

Bilski

A 500 with 44 hp can’t be a steam hammer: the Honda XBR 500 produces 45 Nm at 6000 rpm.

When Honda presented the XBR in 1985 – after a failed attempt called the FT 500 – they stuck to the classic half-liter displacement and in principle relied on an engine design presented in the XR 500 studded steering wheel. And the SRX 6, presented a few months later, took over the complete and only slightly modified engine of the successful Enduro XT 600. So no sensations, but it was as if the motorcycle world was holding its breath for a moment: street motorcycles with large single-cylinder engines. No turbo. No whispering sound. Not 100 hp. And nevertheless …

Anyone who encounters a heavenly premonition somewhere in the Black Forest or Eifel region immediately wants a base that is as light as possible. XBR and SRX are at least light-footed with a full tank of 182 and 172 kilograms, respectively. There are people who then want performance from the wrist. And there are those who demand an engine, want to handle it, want to understand it. From 3000 revolutions the two singles shoot off with full force, whoever chooses the connection at 3500 rpm gains even more thrust. From 6200 rpm the Yamaha becomes tougher, the Honda 500 rpm later.

If things are going to go really fast, 3000 to 3500 tours remain usable speed range. That is not much. But the sheer joy when the driver’s sporting spirit and the course of the road come together. Especially since the periphery fits: they both have easily switchable and, above all, precise gears. Velvety almost with the SRX, a little crisper with the XBR. That in turn can show a more controllable front brake. The game with the mutually distributed small advantages continues: The SRX has the more comfortable, but still stiff chassis, the XBR is more handy. It also turns in a little more precisely.

The view goes over two classically designed instrument consoles, the seating position is sporty, but by no means so radical that it would spoil the view of the beautiful surrounding area. No bulging cylinder heads hinder the knee connection to the adequately (SRX) or generously (XBR) sized tanks. Ease. Yes, it can be that easy. Always back and forth between third and fifth gear and up and down. One gear step lower in hairpin bends, both engines push reliably and without jerking at just under 2000 rpm.

Here as there, a balancer shaft tames the vibrations. In the opinion of some single-cylinder fans, Yamaha proceeded more skillfully because it wasn’t quite as thorough. In fact, the Honda does not know a speed range below around 6000 rpm in which its vibrations can get to the bone. The Yamaha does, and that can be annoying at constant speeds. Next Battle in the War of Faith: Does a Single Need an E-Starter? More precisely: is he even allowed to have one? Honda says yes, although the XBR with its well-dimensioned kick starter starts even better than the SRX. Yamaha says no, which is why jealousy can occasionally arise when the engine is half warm. In addition, the right footrest must be folded up before kicking.

Bilski

Yamaha gets 42 HP and 48 Nm (at 5500 rpm) from the XT 600 engine, which has been slightly drilled out for the SRX.

On the other hand, the starter freewheel is one of the very few XBR weak points – if there is no SRX driver nearby, their fans kick it as a precaution. But it can be said that the engine lasts even longer. You never really need oversized pistons 50,000 kilometers ago, and the steadily running engine also puts less strain on the transmission. Only Yamaha knows pitting on the fifth gear pair. And in doing so, the Honda design ventures much further.

With 88 hp per liter of displacement, the XBR achieved a real top value among approved single-cylinders in 1985, only a few years ago KTM scratched the 100 hp / liter limit – admittedly under drastically strict emissions and noise regulations. The Honda single keeps the secret of its performance in its head: four radially arranged valves, actuated by a camshaft via rocker arms and rocker arms, which release a full cross-section with carefully calculated overlap times. RFVC – Radial Four Valve Combustion Chamber – was the name Honda gave to this design, introduced in 1983 for the Enduros, which enables a high-performance, hemispherical combustion chamber. At a nominal speed of 7000 rpm, the piston speed of the significantly short-stroke engine is 17.5 meters per second. He gets his mixture from a respectable 39 Keihin constant pressure carburetor, the exhaust gases are disposed of by a double exhaust system. Thanks to the two bends, the sensitive outlets receive enough cooling air, but above all the counter pressure remains limited – good for a full filling.

Yamaha also invested a lot of brainpower in the gas exchange of the sohc four-valve engine and prescribed the SRX – as with the Enduro – a Teikei register carburetor: Initially, only the 27-valve carburetor opens to enable high flow speeds thanks to the small cross-section. At 4000 rpm, the equal pressure partner, which is also 27 millimeters in size, is activated. Here, too, it is blown off via two elbows, which, however, open into a large front silencer under the gearbox. There, too, there is only little counter pressure, and the desired tidy overall SRX image can also be achieved. This clever plan worked, just not in Switzerland, where MOTORRAD CLASSIC supported the two main characters in this story. The authorities there demanded that the end piece protruding from the front silencer should be extended.

Both engines open hearts, the 600 with its down-to-earth style, the 500 with its sleek style. The former is more committed to the rough single traditions, the latter more to their dynamic modernization. Typically Honda, many say, and the next chapter also fits into that. Of course, the simple single-tube frame with beams is sufficient in this class. If you thresh the XBR through fast corners with a bumpy surface, you will notice a slight twisting, but you shouldn’t talk about chassis weaknesses. But the Yamaha, which is actually a touch stiffer, simply looks much better with its double loop made of rectangular steel. The beams are screwed on, so not even hobbyists can complain about removing the engine.

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Engine sketches in comparison: Honda XBR 500 (left) and Yamaha SRX 6 (right).

Honda hides the oil tank for the dry sump lubrication behind the right side cover, while at Yamaha it sits enthroned as a finely ribbed object above the transmission. The light SRX rear with box swing arm, imposing disc brake, narrow rear rump and discreet rear light looks like the icing on the cake of an overall closed design. In contrast, the Honda looks as if its designers ran out of time just past the middle. By no means bad, but – in the truest sense of the word – not thought through to the end.

This judgment should have been restricted 25 years ago because the Yamaha was significantly more expensive than the Honda. You could expect tinny side covers and a little more polished metal. Or wheels made of cast light metal instead of those with sheet metal spokes riveted to the rim. Comstar called Honda this invention and made half the model range happy with it. At least in the middle class, the rivets held, and today Comstar wheels have a more contemporary look than the wire spokes that were later offered as an alternative.

Nevertheless, the latter are more popular in the very lively XBR scene. Even with conversions, and there are many. Even one from Honda: The GB 500 Clubman, originally created as a 400 for Japan and then with 500 cc for the US market, inspired many with wire-spoke wheels, more discreet indicators, rear chrome fenders, a narrower rear and 2-in -1 exhaust system XBR creations. The majority tends towards sport, also technically, which is why flat slide carburetors, better bearings for the steering head and swing arm as well as Ikon struts are part of the usual equipment. It remains a matter of dispute whether installing the engine of the Power Enduro XR 600 has more advantages or disadvantages and where you can order a usable 2-in-1 exhaust system.

Such concerns seem to be less of a concern for the SRX community. On the one hand, the tuning topic is written a little smaller, on the other hand, the original look is probably better. The current registration statistics reported 1,100 Yamaha singles, around 2,500 were even sold: the SRX, which was initially so acclaimed, became a grandfather clock towards the end of its life in 1990. The Honda did better, of which 3200 pieces are still listed today – without Clubman. Accordingly, good specimens with a mileage of around 30,000 kilometers are available for 1,500 euros, while the Yamaha can cost three hundred more.

A humble treat, and one of the reasons why some people find it a heavenly one. Some will argue that an SRX with XBR sound would be even more heavenly. They should both buy, one to look at, the other to listen to, both to drive. Through lively alternating curves, hilly landscapes and light spring forest.

Technical specifications

Bilski

The seating position on the Yamaha SRX 6 is a little more stretched than on the Honda XBR 500, but still human-friendly. It also shines with good lean angle and an astonishingly sporty, yet comfortable chassis.

Yamaha SRX 6

Honda XBR 500

engine

type design

Air-cooled single cylinder four-stroke engine, one overhead camshaft, four valves, rocker arms

Air-cooled single cylinder four-stroke engine, one overhead cam-
shaft, oven valves, rocker arm and rocker arm

drilling

96.0 mm

92.0 mm

Hub

84.0 mm

75.0 mm

Displacement

608 cm3

498 cm3

compression

8.5: 1

8.9: 1

power

42 hp at 6500 rpm

44 hp at 7000 rpm

Mixture preparation

Register carburetor,
Teikei, Ø 27 mm each

Constant pressure carburetor, Keihin, Ø 39 mm

ELECTRICAL SYSTEM

starter

Kickstarter

E and kick starter

battery

12 V / 4 Ah

12 V / 12 Ah

ignition

Contactless

Contactless

alternator

Three-phase current, 12 V / 125 W.

Three-phase current, 12 V / 170 W.

POWER TRANSFER

coupling

Multi-disc oil bath clutch

Multi-disc oil bath clutch

transmission

Five-speed, claw shift

Five-speed, claw shift

Primary drive

Gears

Gears

Secondary drive

O-ring chain

O-ring chain

LANDING GEAR

Frame type

Double loop frame made of rectangular tubular steel

Single tube frame made of tubular steel with forked beams

Front wheel guide

Telescopic fork, Ø 36 mm

Telescopic fork, Ø 35 mm

Rear wheel guide

Two-sided swing arm, two struts

Two-sided swing arm, two struts

bikes

Cast light alloy wheels

Light alloy composite wheels

Front tires

100/80 S 18

100/90 S 18

Rear tire

120/80 S 18

110/90 S 18

Front brake

Double pane, 
Ø 270 mm, two-piston fixed calipers

Disc, Ø 274 mm, double piston-
Floating saddle

rear brake

Disc, Ø 245 mm, two-piston fixed caliper

Drum, Ø 140 mm

MASS AND WEIGHT

Weight

172 kg

182 kg

Tank capacity

15 liters

20 liters

Performance

Top speed

170 km / h

171 km / h

PRICE

7130 Mark (1986)

5683 Mark (1985)

MANUFACTURING

Yamaha Motor Co. Ltd, Iwata, Japan

Honda Motor Co. Ltd, Tokyo, Japan

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