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Yamaha SR 500
Road Test 1978
Is progress a red herring? The Yamaha SR500E—lean, clean and crewcut—might make you wonder. Could it be that the swift march of technology is carrying street motorcycles into a future more fanciful than fun? Is it possible that froggy buzzers, blazing lights, digital readouts, instrument clusters, built-in stereos, heated handgrips, rear-view mirrors with electric defrosters, and third, fourth, fifth and sixth cylinders are subversive; or worse, some pinko conspiracy to reduce •true-blue, Type-A-Positive American Manhood to limp vanilla pudding? Will this single-cylinder, you-kick-it-to-life motorcycle rescue our sport? And doesn't the SR500E belong to an era when Dick. Tracy shot the perpetrators square between the eyes without ever reading them their constitutional rights, when Audie Murphy blew away entire enemy regiments in black-and-white war movies, and when Lois Lane would step into a telephone booth with nothing more serious in mind than the Daily Planet's phone number?
Well, sorry. You square-jawed heroes who think Seventies-style motorcycling has gotten soft without sprained ankles and brightly colored hematomas will find little of the 1950s in Yamaha's SR500E. It's not a revival machine that transports the aches and pains and oil leaks of 1952 forward to the threshold of 1980. On the contrary, this 500 single is a thoroughly modern motorcycle.
To say that the concept—an agile 500cc four-stroke single—is "old" misses the point. Sometimes a good idea seems to be frozen in metal, inextricably tied to a particular set of machines in a given time-frame. But a good idea is a really timeless thing. And so the big-bore single-cylinder roadster has come back; rethought, re-engineered and reconstituted in all its mechanical specifics.
Yamaha's new street bike has been developed out of the XT500 and TT500 dirt bikes, but even here the lineage tends to be more apparent than real. The SR500E is not a street-bike adaptation of the XT500. To be sure, TT, XT and SR all have 87 x 84mm engines, and the XT and SR units both have 9.0 to 1 compression ratios and share basic driveline components. However, in many important respects the SR500E engine is a creature unto itself.
The SR500E cylinder head has larger fins for better heat dissipation compared to the XT; and while Yamaha has not changed cam timing, the inlet and exhaust tracts have been reshaped to get better performance. Most of the work has gone into the inlet side of the engine where the SR has a 34mm Mikuni carburetor feeding a 47mm intake valve, compared to the XT's 32mm carb and 45mm poppet. Further changes in the cylinder head include new valve-seat material to improve the durability of the seat when using low-lead or non-leaded gasoline, and the exhaust valve guide has been standardized with the intake guide.
Yamaha has not overlooked the piston. The pin-boss area of the 500's piston has been strengthened, the overall length of the piston has been increased by six millimeters, and Yamaha has modified the piston's oil ring. Street riders probably use more revs over longer time periods with less maintenance than their dirt-riding counterparts, and Yamaha has made all these modifications to guard against excessive oil consumption.
Downstairs in the crankshaft department, Yamaha increased the flywheel capacity by extending the diameter of the crank webs, claiming a benefit in reduced mechanical noise. Moreover, the material in the forged and hardened crankshaft was changed in the redesign.
Cost and appearance considerations probably led to the disappearance of the magnesium side covers found on the dirt singles. Both the left and right side covers on the SR500E are buffed-out aluminum. Yamaha spent their money in other ways: The SR500E has a hoop around the clutch housing to strengthen this component, detail changes have been made to some transmission gears to increase their durability, and the shift pawl and drum have been modified in order to get easier, more positive shifting. Specifically, the toothed primary pawl, instead of being splined to the shift shaft, is integral with the shaft; now there's nothing to loosen or slip. And the shift drum is supported on the left side by a new needle bearing that reduces drum drag and facilitates smooth gear-changing.
The fussing with the crankshaft assembly suggests Yamaha's concern with vibration, a traditional complaint about the big single. That concern shows elsewhere, but not necessarily in a way the casual observer might expect. The XT has one rubber and three solid mounts that attach the engine to the frame, whereas the SR500E, far from being rubber-mounted all the way round, is solidly fixed to the frame at all four points. Enormous soft-rubber bushings, like the old Norton system, would have isolated the thumping vibrations of the 500 single from its frame. Yamaha rejected this complicated and expensive option. Elaborate soft-mounts or counter-rotating balancers were out of the question too; those solutions violated the simplicity and cost-effectiveness that Yamaha wanted in the SR500E. So the engineers did more homework on frame design and solid engine mounting in order to hold the vibration through the frame to an acceptable level.
Outfitting the 500 for street duty included a new frame. The tubework may be based on the XT500, but frame-tube diameters have been increased and key points of the frame have been reinforced to increase rigidity. A strong and fairly massive frame that clinches the engine tightly can carry off engine vibration without fracturing, transmitting some of the pulsing through the suspension to the ground. To illustrate where vibration can go, step back five feet from an idling SR500E, watch the bike move on its suspension, and then put your hand to the pavement—and feel the quaking.
No wonder that the rear fender, gas tank and footpegs are rubber-mounted. In fact, even the caliper mounts for the rear disc brake have rubber bushes to soften the vibration. The battery-box space has been made large to provide more room so that longitudinal vibrations won't rattle the battery against nearby components.
Incidentally, the side cover and battery box have been designed in such a way that both the battery and tools (under. a lockable cover) can be removed from the left side of the bike, and the air cleaner can be pulled out from the right. Because the under-seat items come out the sides of the motorcycle, the seat is bolted in position. It doesn't lift up on hinges.
Compared to the XT500, the SR500E has considerably less rake (27.7 degrees vs. almost 31 degrees) and trail (4.7 inches vs. 5.7 inches), producing a quicker-steering bike. The front and rear suspension units more nearly resemble the components found on the XS650 than those fitted to the XT500. Indeed, the SR500 has no off-road capability with a front fork that travels only 6.0 inches, whereas the XT is good for 7.8 inches. At the rear, very ordinary oil-damped shocks provide 4.4 inches of rear-wheel travel, while the XT500's forward-cant DeCarbon shocks allow the rear wheel 6.4 inches of movement. The SR500E also has a slightly shorter wheelbase (56.25 inches) than the XT's 57-inch span. Not surprising is the fact that the 383-pound SR-E packs 64 more pounds than the XT.
Some of the extra baggage has gone into the electrical system. The SR500E has 12-volt electrics charged by a multi-pole alternating-current magneto, instead of the XT's six-volt system with a direct-current flywheel magneto. And the breaker-points ignition fitted to the XT500 has not been carried over to the SR-E. The roadster has a magnetically triggered CDI to fire the spark plug.
Yamaha has provided more than an energetic spark-maker in order to persuade the SR500E into life. Obviously an electric starter would contradict the notion of a light-and-lithe, simple-and-direct single-cylinder roadster. In addition to the starting lever, there's plenty of gadgetry. First, one manfully gets the kickstart lever under foot, hopefully under cover of a good boot. Of course Yamaha figured some owners would step to the starting drill with frazzled tennies, and so the company took pains to protect its light-footed Customers from the uplifting and crippling effects of The Dread Single Cylinder's Recoil & Backlash Through The Starting Lever, And Subsequent Catapult Over The Moon. Using the compression release which lifts the exhaust valve, one cranks the works over until a little white arc appears in a tiny window at the right outboard side of the overhead camshaft.
Then one flicks the choke lever, provided that the engine is cold, and pushes the white throttle-set knob, located nearby the choke lever, into its up-position. With the ignition switched on, and with care not to crack the twistgrip open, the rider thrusts the starting lever downward and awaits those comforting ka-thunka/ka-thunka sounds to well up from the engine department. Failing that, one again consults the old peekaboo window, gives a macho ah-what-the-hell-l-was-only-kidding shrug, and continues to kick.
Until our test SR500E was broken in fully, and until we learned not to flood the thing (the Mikuni has an accelerator pump), and until experience demonstrated that the throttle-set knob should be trusted to raise the throttle-slide the exact amount, the SR500E would either start on the first or second kick or not at all. One Cycle staffer (not an editor) managed to kick the Yamaha into a deeper and deeper case of moodiness until at last he was squirting sweat and frustration from every pore in his body, and nearly a gallon of sweat collected behind his jacket's tightly secured wrist cuff, waterlogging his right arm all the way to the elbow. Without so much as a burp of encouragement, the SR-E refused to push/bump start, and the hapless novice only succeeded in leaping aboard from the left side, skidding the rear wheel, and toppling over—bike and all—into a steaming, cursing heap.
The Yamaha never so cursed the life of the editorial staffers, and firing off the SR500E was simple and easy—after learning what to do, and what not to do. In fact, the neatest trick in the whole start-up routine is resetting the start-throttle knob. The rider just rolls the twistgrip back against its fast-idle position, thus returning the throttle-set button to its off-position. Thereafter, the engine always drops down to its 850- 900 rpm slow-idle speed.
Everyone who rode the SR500E agreed: The motorcycle is enormous fun. Not an awesome motorcycle, not dazzling, not brilliant—but fun. Those riders who have grown up on electric-start twins and fours were intrigued by the single-cylinder Yamaha because it represents a different approach to connecting Points A and B on tarmac. The SR500E is a machine of essentials; a responsive, glove-fit motorcycle.
That motorcycling concept may be fun, but in the real world sometimes being fun isn't enough. After all, steam calliopes are fun, Excalibur roadsters are fun, fifty-year-old two-wheeled crocks are fun. But any modern single-cylinder motorcycle must meet the hard test of reality. What can it do? How does it perform? To make sense in a world of thousand-dollar kick-start twins from Honda, Kawasaki, Suzuki and Yamaha, the $1500 SR500E must perform better in some dimensions than the econo-twins. Granted, you can't buy anything like the SR-E from another source; Yamaha has the corner on the 500cc single-cylinder roadster market. Nevertheless, a 50 per cent premium is a lot to pay just to be different.
In functional terms, the SR500E starts with substantial advantages. It is a specialty motorcycle, a fairly narrow-focus machine, and isn't subject to the kinds of compromises that econo-twins must unavoidably make. Consider the simple matter of seating. In order to attract a broad range of customers, the 400 twins must offer reasonably comfortable accommodations for passengers, and this strategy dictates fairly long, heavy, cushy seats. On the other hand, the Yamaha SR500E is basically a monoposto device, scaled to one person.
Yamaha has capitalized on this seeming limitation. In the first place, the distance between the seat and the rider's footpegs is great enough for real leg room: no semi-double-back positioning.
The relationship between the pegs, bars and seat is genuinely comfortable, and staffers—to a man—liked the riding position. Since a single-cylinder 500 is a relatively tall and narrow motorcycle, the rider gets reasonable saddle height, vertical roominess and a great deal of Ground Clearance. Because the engine is slim, the pegs can be located inboard. and the tank is Mr. Trim. Comfortable? You bet. There's no Fat Albert tank to splay the rider's legs out in a frog-like stance.
The SR500E gives the rider something more than a well-scaled platform; once underway, he discovers that there's usable power. Usable power isn't the stuff that comes blazing out of some little twin at 7500 to 10,000 rpm. Rather, the Yamaha 500 pulls decisively from 3000 rpm; there's enough authority on tap at 3500 rpm to make gear-changing strictly optional. This kind of power won't establish new quarter-mile records for 500s, and the SR-E feels strained and out-of-breath above 75 mph. But with the Yamaha's deep-rpm power a rider is able to get into a natural cadence and rhythm with a winding road that rolls on mile after mile with 45 to 75 mph corners. Since he doesn't have to tap-dance the shift lever all the time, the rider is left free to concentrate on his line through the next corner—or the trees and flowers if he's so inclined.
The SR-E lets you take a good crack at corners. The narrow motorcycle almost seems to make any road about two feet wider than normal. And assuming you approach a corner too hot, the SR-E can brake with vengeance, right to the limit of your confidence in the front tire or its adhesion, whichever occurs first. The hydraulics, front and rear, are first-rate; some riders may skid the rear end but an oversensitive rear disc won't be the cause of the problem.
The nimble Yamaha responds quickly to rider inputs, but its quick responses seem more a function of its light weight and mass placement (relatively high), rather than the result of steering geometry. While the SR500E can be dialed into corners quickly, its basic slow-steering geometry (and chassis rigidity) keep the motorcycle feeling rock-steady through corners. High-technology twins and fours, both 400s and 550s, must—thanks to their weight—get quick input-response via chassis geometry, and this can leave those motorcycles feeling less than perfectly stable through rough 75-mph corners. By comparison, the Yamaha single has an almost Ducati-like quality in its through-the-twisties stability.
While the suspension is compliant, the SR-E doesn't have the velour ride-softness that characterizes bikes like the XS11. The single feels bucky and harsh on the concrete slabbing of freeways. Whipped through bumpy corners, the stiffish rear springs will allow the SR500E to skitter its rear end a little toward the outside of the corner as the rear tire momentarily loses contact with the pavement. Handlebar waggle, dead-reardamper floatiness, and suspension wallowing are all happily absent. And that's what you'd expect, given the Yamaha's weight (383 pounds) and its modest horsepower output.
Because the SR-E has a great deal of Ground Clearance, we suspect that the SR-E's Bridgestone tires, patterned after the old Dunlop Gold Seal rubber, set the bike's outer boundary for corner-carving. The tread design looks dated, but within the parameters of street riding we can't quarrel with performance of the tires.
No matter where or how you ride the SR500E, you'll discover that the seat will begin to burn a hole in your backside within 150 miles. Were it not for the excellent riding position, the SR-E would probably become wearisome inside of 75 miles. For a specialty motorcycle that works best on a Sunday afternoon's ride, a comfort-to-misery point at 150 miles is acceptable. In no case is it possible to ride the motorcycle 175 miles non-stop. Generally, the bike went on its reserve gasoline supply at 135 to 140 miles, returning about 53 mpg. The only gasoline-station hassle was the SR500E's leaky filler cap.
Vibration-fatigue, you might think, far more than burning buttocks would signal an end to a day's riding. Not true. Of course the bike vibrates; the rider feels it through the seat, bars and pegs. But the vibes do not lullaby your extremities to sleep or numb your reflexes. Big-single vibrations are low-frequency, high-amplitude quakings that aren't nearly so insidious as the electric-drill machinations of high-output two-strokes. Unlike vintage 500 singles, the Yamaha does not spray loose nuts and bolts and shed parts at 60 mph. Only one license-plate fastener escaped during the test period.
By design the SR-E is not Everyman's Motorcycle. Prospective owners should test-ride this motorcycle to verify that they can start it, ignore its vibration, enjoy its agility, accept its modest output, and revel in its handling, braking and usable power. If you can use the SR-E, then you'll understand that it's a $1500 motorcycle.
And don't let anybody tell you the SR500E is just a funky revival of England's Grand Old Gold Star. Funky, yes; fun, certainly; repli-revival, no way. The SR500E is a modern five-star remake of a timeless idea
Source Cycle 1978