Post by Pardee on Jun 25, 2014 13:54:28 GMT -5
Cycle World Road Test--Sept. 1973
Yamaha TX500
Headline: Yamaha laid down a mandamus to its engineers:
Build us a four-stroke 500 twin that charms...and they did!
Text:
Until the introduction of the XS-1 650cc sohc vertical Twin in 1970, Yamaha's entire production was of two-stroke motorcycles. These ranged in size from the 50cc Single to the 350cc Twin, and there were models which suited the commuter, the trail rider and the sports oriented street rider just fine. But the long distance touring buff was left without a suitable mount.
The XS-1 was a step in the right direction, but it suffered from one of the shortcomings of most four-stroke vertical twins: vibration. Yamaha corrected this, however, with the introduction of the TX750, and the subject of this test, the super trick TX500.
We realize that the word "trick" is usually reserved for modified machines, but in the case of the TX500 it is equally appropriate. Here's why. The 500cc vertical Twin that powers the TX has twin overhead camshafts, four valves per cylinder,. an electric starter and an Omni-phase balancer to control vibration. That alone is enough to place the machine in the trick category, but there's more. There is a disc brake up front and somehow Yamaha engineers have fit all this in a machine not much larger than their RD350 two-stroke.
At first glance, in fact, the TX500 looks very similar to the Yamaha RD350 Twin. The seat, gasoline tank and headlights look very much the same, and once aboard, the seating positions are very similar, too. Not surprisingly, the handling characteristics are also similar, although the TX500 is several pounds heavier, tipping the scales at 433 lb. ready to go with a half tank of fuel.
Starting the TX500 is decidedly simple. Switch on the ignition, close the choke lever, press the starter button and the engine bursts to life almost immediately. Soon it settles down to a smooth idle, with very little mechanical noise. After a brief warm-up, low gear can be selected and one of the smoothest rides of a machine of this configuration can be begun.
The ordinarily round steel clutch plates are flattened somewhat between the outer third of each plate and these are installed with the flattened portions 120-deg. apart to eliminate the rattle when the clutch lever is withdrawn. Seven of these plain plates and eight plates with a bonded on lining give plenty of total area to prevent clutch slip, even under hard acceleration.
Spacing between the transmission's five ratios is close to ideal and shifting effort is held to a minimum by a precisely machined shifting drum no shifter fork arrangement, Gearshift lever travel is short and positive, adding to the snug feeling of the machine.
The engine unit itself is fairly compact considering the number of components inside. Following racing automobile practice, all the bearings in the power producing section are plain bearings. The crankshaft rides on three plain main bearings, the connecting rod big end bearings have babbitt-type inserts and the small end bearings which support the piston pins are plain bushes. Even the twin overhead camshafts, which are steel, ride in plain bearings in the aluminum supports.
Ball bearings support the transmission shafts, however, and the oil for both the engine and transmission is circulated by an Eaton-type variable displacement pump with twin rotors to ensure a copious supply of oil to both lubricate and cool the moving parts of the engine.
One of the first things you notice about the TX500 is the very low vibration level. This is brought about by the use of the Omni-phase balancer which has counterweights to cancel out the main flywheels' imbalance, but unlike the TX750, only on shaft with two bobweights is used. There is still some vibration, but it is of such low magnitude that it is not bothersome at any speed above 2500 rpm right up to the 9000 rpm red-line.
Rakishly upswept mufflers emit only a whisper, engine noise is very low and intake roar when the throttle is opened wide is not objectionable. At a steady 70 mph the loudest noise you hear is the wind rushing past your helmet!
Controls are all well placed, with the handlebar switches clearly labeled to avoid confusion. The left hand switches are the horn button, turn signal switch and the headlight high/low beam control. The right hand controls are the headlight on/off switch, and electric starter button and an off/run/off switch to stop the engine in the unlikely event of a throttle malfunction. Unlike some motorcycles we've tested lately, all the switches are within easy reach of the rider's thumbs, and worked perfectly every time.
The instrument panel contains a large speedometer and tachometer, nicely illuminated at night by a soft green glow. The non-glare resistant glass lenses, however, reflect sunlight right into the rider's eyes during the day. A stoplight indicator and an oil pressure light are red in color and can be clearly seen at all times, but the yellow turn signal indicators are difficult to see on a sunny day. The ignition switch is located where it should be: right in the middle of the instrument panel and the key not only serves to turn on the ignition, it also unlocks the gasoline filler cap, the seat and the steering head locks.
As mentioned earlier, the TX500 handles very much like its smaller brother, the RD350. Fairly low handlebars contribute to the nearly perfect starting position and foot peg location to make the machine a joy to ride around town and at a fast clip on swervy roads. The only part of the layout we could find fault with was the seat, which is too hard (from a lack of sufficient padding) for extended periods of cruising in a straight line. Oddly enough, we received no complaints from our passengers who spend as much as two hours on their half of the seat.
Of interest to the sporting rider are the brakes. The rear is a conventional drum type which, in spite of its rather small size, is very powerful and highly resistant to fade. The front disc brake is superlative in operation. A handlebar-mounted master cylinder is acted upon directly by the front brake lever and forces the brake fluid down to a double-acting caliper unit which forces the pads against the brake disc without having to have a floating, self-aligning caliper.
There are lugs already cast into the left hand fork leg to mount a similar caliper to the other side for those riders who prefer ever more braking power than the standard setup. We feel that the single disc is more than adequate and even after more than half a dozen panic stops from 60 mph during our braking tests we didn't note any appreciable fade. In addition, the disc brake components are lighter in weight than a drum brake with similar stopping power, reducing the unsprung weight which so seriously affects handling.
Also important to the handling qualities of a motorcycle are the suspension components. The front forks provide 5.5-in. of travel and even though they are sprung on the soft side for comfort, both compression and rebound damping are adjusted to provide good roadholding characteristics, even over rough pavement. The rear suspension components are getting better on Japanese machines, but with the springs in their lowest (softest) position, the machine would wallow slightly in fast turns. Jacking the spring adjustment up all the way stiffened up the ride a little but made the machine more stable when blasting through bumpy turns. Also, with the springs in the softest position there was the feeling that the bike was hinged in the middle under difficult turn conditions, but this feeling almost disappeared when the springs were stiffened up.
On a warm afternoon we began an extended trip which included about 50 miles of freeway riding. The front forks were sensitive enough to absorb the small ripples where the sections of concrete are joined, and the grooved pavement stretches on some California freeways didn't cause the machine to wander.
A small complaint we had regarding the difficulty of riding the machine smoothly was directly related to the push-pull throttle arrangement. Two cable emerge from opposite sides of the throttle control with one pulling the throttle open and the other pulling it closed when the throttle grip is turned forward. In theory, this arrangement works fine; but even with careful adjustment of the cables there was always enough free play to make precise throttle control at low openings almost impossible. Add to this is the slack in the drive train (caused by the cushioning springs in the clutch hub which lessens shock to transmission gears and the rubber blocks in the rear wheel hub between it and the rear sprocket) and the ride was jerky unless great care was used when opening and closing the throttle.
The overall finish of the TX500 is absolutely first-rate. Chromium-plated fenders, exhaust pipes and mufflers, wheel rims and handlebars are set off by beautifully applied paint (bronze, gold and black in this case) with no runs or imperfections anywhere. The fiberglass side covers are easily detachable to give access to the bulk of the electrical wiring and tool kit, and the battery is easily serviced by raising the seat.
Electrical components are also without fault, Most of the wiring is concealed to protect it from damage, and the lights are more than adequate for traveling at legal speeds at night. The only complaint we had was the horn. At 60 mph, blowing the horn could hardly be heard by the rider, much less by a person in an automobile or a pedestrian.
Many nice touches are evident, like the allen head screws which replace the phillips head screws on the engine sidecovers and rocker box assembly. An oil filter canister which removes impurities from the engine/transmission oil is located behind the countershaft sprocket cover and just below the countershaft sprocket. The air cleaner element is quite large and is easy to remove for cleaning or replacement by lifting up the seat and removing a snap-on cover.
Generally speaking, the Yamaha TX500 is a notable newcomer to this displacement category, both in its degree of refinement and execution. Generalities aside, it a machine a lot of people have been wanting for for a long time--a 500 Twin in classic configuration, incorporating the latest technical advances of the '70s.
Article includes several photos, tech specs and performance test results.
Yamaha TX500
Headline: Yamaha laid down a mandamus to its engineers:
Build us a four-stroke 500 twin that charms...and they did!
Text:
Until the introduction of the XS-1 650cc sohc vertical Twin in 1970, Yamaha's entire production was of two-stroke motorcycles. These ranged in size from the 50cc Single to the 350cc Twin, and there were models which suited the commuter, the trail rider and the sports oriented street rider just fine. But the long distance touring buff was left without a suitable mount.
The XS-1 was a step in the right direction, but it suffered from one of the shortcomings of most four-stroke vertical twins: vibration. Yamaha corrected this, however, with the introduction of the TX750, and the subject of this test, the super trick TX500.
We realize that the word "trick" is usually reserved for modified machines, but in the case of the TX500 it is equally appropriate. Here's why. The 500cc vertical Twin that powers the TX has twin overhead camshafts, four valves per cylinder,. an electric starter and an Omni-phase balancer to control vibration. That alone is enough to place the machine in the trick category, but there's more. There is a disc brake up front and somehow Yamaha engineers have fit all this in a machine not much larger than their RD350 two-stroke.
At first glance, in fact, the TX500 looks very similar to the Yamaha RD350 Twin. The seat, gasoline tank and headlights look very much the same, and once aboard, the seating positions are very similar, too. Not surprisingly, the handling characteristics are also similar, although the TX500 is several pounds heavier, tipping the scales at 433 lb. ready to go with a half tank of fuel.
Starting the TX500 is decidedly simple. Switch on the ignition, close the choke lever, press the starter button and the engine bursts to life almost immediately. Soon it settles down to a smooth idle, with very little mechanical noise. After a brief warm-up, low gear can be selected and one of the smoothest rides of a machine of this configuration can be begun.
The ordinarily round steel clutch plates are flattened somewhat between the outer third of each plate and these are installed with the flattened portions 120-deg. apart to eliminate the rattle when the clutch lever is withdrawn. Seven of these plain plates and eight plates with a bonded on lining give plenty of total area to prevent clutch slip, even under hard acceleration.
Spacing between the transmission's five ratios is close to ideal and shifting effort is held to a minimum by a precisely machined shifting drum no shifter fork arrangement, Gearshift lever travel is short and positive, adding to the snug feeling of the machine.
The engine unit itself is fairly compact considering the number of components inside. Following racing automobile practice, all the bearings in the power producing section are plain bearings. The crankshaft rides on three plain main bearings, the connecting rod big end bearings have babbitt-type inserts and the small end bearings which support the piston pins are plain bushes. Even the twin overhead camshafts, which are steel, ride in plain bearings in the aluminum supports.
Ball bearings support the transmission shafts, however, and the oil for both the engine and transmission is circulated by an Eaton-type variable displacement pump with twin rotors to ensure a copious supply of oil to both lubricate and cool the moving parts of the engine.
One of the first things you notice about the TX500 is the very low vibration level. This is brought about by the use of the Omni-phase balancer which has counterweights to cancel out the main flywheels' imbalance, but unlike the TX750, only on shaft with two bobweights is used. There is still some vibration, but it is of such low magnitude that it is not bothersome at any speed above 2500 rpm right up to the 9000 rpm red-line.
Rakishly upswept mufflers emit only a whisper, engine noise is very low and intake roar when the throttle is opened wide is not objectionable. At a steady 70 mph the loudest noise you hear is the wind rushing past your helmet!
Controls are all well placed, with the handlebar switches clearly labeled to avoid confusion. The left hand switches are the horn button, turn signal switch and the headlight high/low beam control. The right hand controls are the headlight on/off switch, and electric starter button and an off/run/off switch to stop the engine in the unlikely event of a throttle malfunction. Unlike some motorcycles we've tested lately, all the switches are within easy reach of the rider's thumbs, and worked perfectly every time.
The instrument panel contains a large speedometer and tachometer, nicely illuminated at night by a soft green glow. The non-glare resistant glass lenses, however, reflect sunlight right into the rider's eyes during the day. A stoplight indicator and an oil pressure light are red in color and can be clearly seen at all times, but the yellow turn signal indicators are difficult to see on a sunny day. The ignition switch is located where it should be: right in the middle of the instrument panel and the key not only serves to turn on the ignition, it also unlocks the gasoline filler cap, the seat and the steering head locks.
As mentioned earlier, the TX500 handles very much like its smaller brother, the RD350. Fairly low handlebars contribute to the nearly perfect starting position and foot peg location to make the machine a joy to ride around town and at a fast clip on swervy roads. The only part of the layout we could find fault with was the seat, which is too hard (from a lack of sufficient padding) for extended periods of cruising in a straight line. Oddly enough, we received no complaints from our passengers who spend as much as two hours on their half of the seat.
Of interest to the sporting rider are the brakes. The rear is a conventional drum type which, in spite of its rather small size, is very powerful and highly resistant to fade. The front disc brake is superlative in operation. A handlebar-mounted master cylinder is acted upon directly by the front brake lever and forces the brake fluid down to a double-acting caliper unit which forces the pads against the brake disc without having to have a floating, self-aligning caliper.
There are lugs already cast into the left hand fork leg to mount a similar caliper to the other side for those riders who prefer ever more braking power than the standard setup. We feel that the single disc is more than adequate and even after more than half a dozen panic stops from 60 mph during our braking tests we didn't note any appreciable fade. In addition, the disc brake components are lighter in weight than a drum brake with similar stopping power, reducing the unsprung weight which so seriously affects handling.
Also important to the handling qualities of a motorcycle are the suspension components. The front forks provide 5.5-in. of travel and even though they are sprung on the soft side for comfort, both compression and rebound damping are adjusted to provide good roadholding characteristics, even over rough pavement. The rear suspension components are getting better on Japanese machines, but with the springs in their lowest (softest) position, the machine would wallow slightly in fast turns. Jacking the spring adjustment up all the way stiffened up the ride a little but made the machine more stable when blasting through bumpy turns. Also, with the springs in the softest position there was the feeling that the bike was hinged in the middle under difficult turn conditions, but this feeling almost disappeared when the springs were stiffened up.
On a warm afternoon we began an extended trip which included about 50 miles of freeway riding. The front forks were sensitive enough to absorb the small ripples where the sections of concrete are joined, and the grooved pavement stretches on some California freeways didn't cause the machine to wander.
A small complaint we had regarding the difficulty of riding the machine smoothly was directly related to the push-pull throttle arrangement. Two cable emerge from opposite sides of the throttle control with one pulling the throttle open and the other pulling it closed when the throttle grip is turned forward. In theory, this arrangement works fine; but even with careful adjustment of the cables there was always enough free play to make precise throttle control at low openings almost impossible. Add to this is the slack in the drive train (caused by the cushioning springs in the clutch hub which lessens shock to transmission gears and the rubber blocks in the rear wheel hub between it and the rear sprocket) and the ride was jerky unless great care was used when opening and closing the throttle.
The overall finish of the TX500 is absolutely first-rate. Chromium-plated fenders, exhaust pipes and mufflers, wheel rims and handlebars are set off by beautifully applied paint (bronze, gold and black in this case) with no runs or imperfections anywhere. The fiberglass side covers are easily detachable to give access to the bulk of the electrical wiring and tool kit, and the battery is easily serviced by raising the seat.
Electrical components are also without fault, Most of the wiring is concealed to protect it from damage, and the lights are more than adequate for traveling at legal speeds at night. The only complaint we had was the horn. At 60 mph, blowing the horn could hardly be heard by the rider, much less by a person in an automobile or a pedestrian.
Many nice touches are evident, like the allen head screws which replace the phillips head screws on the engine sidecovers and rocker box assembly. An oil filter canister which removes impurities from the engine/transmission oil is located behind the countershaft sprocket cover and just below the countershaft sprocket. The air cleaner element is quite large and is easy to remove for cleaning or replacement by lifting up the seat and removing a snap-on cover.
Generally speaking, the Yamaha TX500 is a notable newcomer to this displacement category, both in its degree of refinement and execution. Generalities aside, it a machine a lot of people have been wanting for for a long time--a 500 Twin in classic configuration, incorporating the latest technical advances of the '70s.
Article includes several photos, tech specs and performance test results.