Post by Pardee on Jun 25, 2014 13:18:02 GMT -5
TEST: The Yamaha TX750
"Not just a face lift, but a whole new package."
Modern Cycle, December 1972
Small wonder that Yamaha's offer to road test their new 750 was met with polite indifference; their all new top-of-the-line model is powered by a twin! And it's not even an interesting sort of twin, such as a V or opposed layout. It's a garden-variety vertical (well almost) side-by-side two-cylinder engine that was an exciting design concept perhaps thirty or forty years ago. Whoopee!
In case you haven't already detected it, the chiding is done tongue in cheek. Despite the prosaic cylinder arrangement the Yamaha 750 promises to be one of the great motorcycles. Yes, great! It does what is expected of a large displacement roadster, better than most, and it provides a great deal of fun in the process.
The most striking feature of the new 750 is the engine package, a dramatic departure from Yamaha's British-like 650. The cobby appearance has given way to a smooth, one piece look that is, at first glance, a bit appliance like. But certainly there's more to the new engine than a cosmetic facelift; it is totally new from the crankshaft out. Most important, of course, is the engine's performance, out of the box it's not spectacular, but it is strong throughout its range and extremely well mannered. However, the potential - particularly on a Class C contender - is undeniable. Great things may be expected of this engine in the hands of capable tuners.
As with most Japanese engines the cases are split horizontally. Consequently, the engine remains clean and oil free. Even the external oil lines to and from the remote oil tank don't foul the exterior with seeping oil. There is nothing in the 750's design that is particularly startling - just excellent execution of good engineering concepts. Such as a single overhead cam chain driven at its center - which operates the valves through rockers. Valve adjustment is a piece of cake through generous ports that are covered by old-time-y individual hex-head covers.
Wisely, Yamaha has chosen Solex constant velocity carburetors. Their performance throughout the operating range - from starting, through idle, during hard acceleration, and at constant mid-range speeds, hot or cold - just can't be faulted. Power transition from deceleration to acceleration is smooth and always predictable. The air filter box appears small for an engine this size, but if its hurting the Yamaha's performance it's difficult to tell.
Counter to the trend to one-piece exhaust systems, Yamaha have fitted a most handsome two-piece unit to their new twin (that's two pieces a side). Despite this there is no evidence of leakage at the joints. A finned cast exhaust manifold precludes the use of a balance pipe and offers added heat dissipation at a critical point. The head pipes are stout and are connected to the manifold with a pair of snug collars. The mufflers are seamless, handsome, and well finished. Exhaust noise is very low and the note is pleasantly throaty and even.
The 750 is remarkably smooth for a 360-degree twin. This due in great part to chain-driven counter rotating weights located in the transmission cavity. At idle this mechanism sounds like a small marimba band, but in light of what it accomplishes it's a small price to pay and a trait that one soon gets used to.
The oil pump shaft is driven off the main engine gear and also provides the ignition's point drive. A special, and very expensive looking 3,000-mile oil filter is concealed behind the left side rear engine cover. The oil tank is located on the right side in the triangle of the main and rear sub-frame. The oil fill pipe and dipstick are located under the seat and the tank drain is conveniently placed beneath the oil tank, exposed on the right side.
Push-button starting is quick and reliable. The alternator easily keeps the battery charge level up even during sustained night riding. And should something go amiss with the electric starting system the kick-starter can be trusted to twist the engine to life with only a moderate amount of effort.
The clean outer engine cases are held in place with allen head screws, and are free from leaks and seepage. Cooling vents are cast into the left side cover to permit air stream cooling of the alternator. The total effect of design and finish make this one of the best looking power plants on the market.
Capital has been made of the engine's broad torque range with selection of the gear ratios. Spacing is close throughout the five speeds with a noticeable absence of the customary tractor-like first gear for two-up tourers. Despite first gear being so close to second, the engine moves the motorcycle off the mark smartly, without clutch slippage or throttle fuss.
Gear selection is smooth, but requires positive pedal movement to avoid rare, occasional, unwanted neutral. The wanted neutral, incidentally, is almost never found with the engine running - cold or hot. The only drill we found workable was to hook the front of the selector with the heel, snap it up smartly into second and then fairy-tap it into neutral. A good deal of practice is required before the green indicator can be counted on to light nearly every time. We don't know if this is a correctable fault, or even one that will plague later production units; our test bike is one of three that were sent over for evaluation, and it bears a low production number for a unit that is this well turned out.
Gear ratios and overall transmission characteristics nicely suit the racer potential of the engine, and further compliment a superb handling chassis. The main frame is just as new as the engine, and just as good in its department. It's a robust structure, well triangulated and nicely welded. Gusseting has been applied in the interests of strength and rigidity, if not for light weight.
The passenger peg-muffler mounting struts are tubular - a nice improvement over the fabricated stampings that have been used on previous Yamaha biggies.
At almost 59 inches the 750's wheel-base is long. Low speed handling, however, is not adversely affected and, in fact, the Yamaha rates very high as a good all-around city transport. Suspension on both ends favors the soft side but is definitely not mushy. Damping is good and well suited to the spring rates and the motorcycle's weight. A total absence of bound-rebound sharpness keeps the 750 tracking true and steady under all surface conditions, during hard cornering and full throttle acceleration. The front end is set up with very little trail, and as a result the Yamaha steers neutrally and with great sensitivity. Cornering line alterations are achieved very easily with body english, and in the opinion of at least one very knowledgeable and well-experienced tester the 750's handling quickness may produce anxious moments for eager but moderately experienced riders. In no way can this be considered a fault of the motorcycle; ridden as it should be it is a safe, stable handler that must be ranked with the very best tourers, past and present. In the hands of the race-wise and long-experienced; the Yamaha is nothing short of brilliant - an honest-to-goodness superbike in all aspects, and not just in straight-line running.
As might be hoped for on such a strong performer, the 750 is blessed with a fairly balanced set of brakes. The front disc is quiet and efficient with good hydraulic advantage. The rear drum evidenced an acceptable amount of fading after several miles of hard usage on a twisting downhill section of mountain road. Still, it was able to assist the front unit in hauling the Yamaha down to walking speed to negotiate surprise hairpins. The rear unit is fitted with an intrumented sensor that warns of inadequate lining thickness, so we're told; several thousand miles of use are required to wear the lining down to the point that the indicator is activated.
Instrumentation on this motorcycle is as good as we've seen. Particularly good are the directional indicators which are located in full view at the top of the panel, very bright and visible even in sunlight. Immediately beneath the indicator is a white lamp labeled simply "LAMP" that had us puzzled until it was discovered that the high-beam/low-beam switch has an intermediate position for both beams at which point the "LAMP" lamp lights. And at which point the headlamp burns a great hole into the darkness. An excellent touch!
Riding position and controls relationship are excellent for average to large physiques and acceptable for the moderately short rider. With the exception of some roughness on one of the outer engine cases, the finish on plated and polished components is of high standard. The high metallic paint is a little garish - not nearly so handsome as the scheme as used on the 650's, but that's pretty subjective and also a bit niggling.
Our association with the Yamaha 750 ended much differently than it began. Our mildly indifferent reaction to its announcement at the beginning has been altered through getting to know it, to enthusiastic fondness for this superbly conceived and executed motorcycle. The only note of disappointment arose after all the testing and poking and prodding had come to an end, and that was when Yamaha took it back.
"Not just a face lift, but a whole new package."
Modern Cycle, December 1972
Small wonder that Yamaha's offer to road test their new 750 was met with polite indifference; their all new top-of-the-line model is powered by a twin! And it's not even an interesting sort of twin, such as a V or opposed layout. It's a garden-variety vertical (well almost) side-by-side two-cylinder engine that was an exciting design concept perhaps thirty or forty years ago. Whoopee!
In case you haven't already detected it, the chiding is done tongue in cheek. Despite the prosaic cylinder arrangement the Yamaha 750 promises to be one of the great motorcycles. Yes, great! It does what is expected of a large displacement roadster, better than most, and it provides a great deal of fun in the process.
The most striking feature of the new 750 is the engine package, a dramatic departure from Yamaha's British-like 650. The cobby appearance has given way to a smooth, one piece look that is, at first glance, a bit appliance like. But certainly there's more to the new engine than a cosmetic facelift; it is totally new from the crankshaft out. Most important, of course, is the engine's performance, out of the box it's not spectacular, but it is strong throughout its range and extremely well mannered. However, the potential - particularly on a Class C contender - is undeniable. Great things may be expected of this engine in the hands of capable tuners.
As with most Japanese engines the cases are split horizontally. Consequently, the engine remains clean and oil free. Even the external oil lines to and from the remote oil tank don't foul the exterior with seeping oil. There is nothing in the 750's design that is particularly startling - just excellent execution of good engineering concepts. Such as a single overhead cam chain driven at its center - which operates the valves through rockers. Valve adjustment is a piece of cake through generous ports that are covered by old-time-y individual hex-head covers.
Wisely, Yamaha has chosen Solex constant velocity carburetors. Their performance throughout the operating range - from starting, through idle, during hard acceleration, and at constant mid-range speeds, hot or cold - just can't be faulted. Power transition from deceleration to acceleration is smooth and always predictable. The air filter box appears small for an engine this size, but if its hurting the Yamaha's performance it's difficult to tell.
Counter to the trend to one-piece exhaust systems, Yamaha have fitted a most handsome two-piece unit to their new twin (that's two pieces a side). Despite this there is no evidence of leakage at the joints. A finned cast exhaust manifold precludes the use of a balance pipe and offers added heat dissipation at a critical point. The head pipes are stout and are connected to the manifold with a pair of snug collars. The mufflers are seamless, handsome, and well finished. Exhaust noise is very low and the note is pleasantly throaty and even.
The 750 is remarkably smooth for a 360-degree twin. This due in great part to chain-driven counter rotating weights located in the transmission cavity. At idle this mechanism sounds like a small marimba band, but in light of what it accomplishes it's a small price to pay and a trait that one soon gets used to.
The oil pump shaft is driven off the main engine gear and also provides the ignition's point drive. A special, and very expensive looking 3,000-mile oil filter is concealed behind the left side rear engine cover. The oil tank is located on the right side in the triangle of the main and rear sub-frame. The oil fill pipe and dipstick are located under the seat and the tank drain is conveniently placed beneath the oil tank, exposed on the right side.
Push-button starting is quick and reliable. The alternator easily keeps the battery charge level up even during sustained night riding. And should something go amiss with the electric starting system the kick-starter can be trusted to twist the engine to life with only a moderate amount of effort.
The clean outer engine cases are held in place with allen head screws, and are free from leaks and seepage. Cooling vents are cast into the left side cover to permit air stream cooling of the alternator. The total effect of design and finish make this one of the best looking power plants on the market.
Capital has been made of the engine's broad torque range with selection of the gear ratios. Spacing is close throughout the five speeds with a noticeable absence of the customary tractor-like first gear for two-up tourers. Despite first gear being so close to second, the engine moves the motorcycle off the mark smartly, without clutch slippage or throttle fuss.
Gear selection is smooth, but requires positive pedal movement to avoid rare, occasional, unwanted neutral. The wanted neutral, incidentally, is almost never found with the engine running - cold or hot. The only drill we found workable was to hook the front of the selector with the heel, snap it up smartly into second and then fairy-tap it into neutral. A good deal of practice is required before the green indicator can be counted on to light nearly every time. We don't know if this is a correctable fault, or even one that will plague later production units; our test bike is one of three that were sent over for evaluation, and it bears a low production number for a unit that is this well turned out.
Gear ratios and overall transmission characteristics nicely suit the racer potential of the engine, and further compliment a superb handling chassis. The main frame is just as new as the engine, and just as good in its department. It's a robust structure, well triangulated and nicely welded. Gusseting has been applied in the interests of strength and rigidity, if not for light weight.
The passenger peg-muffler mounting struts are tubular - a nice improvement over the fabricated stampings that have been used on previous Yamaha biggies.
At almost 59 inches the 750's wheel-base is long. Low speed handling, however, is not adversely affected and, in fact, the Yamaha rates very high as a good all-around city transport. Suspension on both ends favors the soft side but is definitely not mushy. Damping is good and well suited to the spring rates and the motorcycle's weight. A total absence of bound-rebound sharpness keeps the 750 tracking true and steady under all surface conditions, during hard cornering and full throttle acceleration. The front end is set up with very little trail, and as a result the Yamaha steers neutrally and with great sensitivity. Cornering line alterations are achieved very easily with body english, and in the opinion of at least one very knowledgeable and well-experienced tester the 750's handling quickness may produce anxious moments for eager but moderately experienced riders. In no way can this be considered a fault of the motorcycle; ridden as it should be it is a safe, stable handler that must be ranked with the very best tourers, past and present. In the hands of the race-wise and long-experienced; the Yamaha is nothing short of brilliant - an honest-to-goodness superbike in all aspects, and not just in straight-line running.
As might be hoped for on such a strong performer, the 750 is blessed with a fairly balanced set of brakes. The front disc is quiet and efficient with good hydraulic advantage. The rear drum evidenced an acceptable amount of fading after several miles of hard usage on a twisting downhill section of mountain road. Still, it was able to assist the front unit in hauling the Yamaha down to walking speed to negotiate surprise hairpins. The rear unit is fitted with an intrumented sensor that warns of inadequate lining thickness, so we're told; several thousand miles of use are required to wear the lining down to the point that the indicator is activated.
Instrumentation on this motorcycle is as good as we've seen. Particularly good are the directional indicators which are located in full view at the top of the panel, very bright and visible even in sunlight. Immediately beneath the indicator is a white lamp labeled simply "LAMP" that had us puzzled until it was discovered that the high-beam/low-beam switch has an intermediate position for both beams at which point the "LAMP" lamp lights. And at which point the headlamp burns a great hole into the darkness. An excellent touch!
Riding position and controls relationship are excellent for average to large physiques and acceptable for the moderately short rider. With the exception of some roughness on one of the outer engine cases, the finish on plated and polished components is of high standard. The high metallic paint is a little garish - not nearly so handsome as the scheme as used on the 650's, but that's pretty subjective and also a bit niggling.
Our association with the Yamaha 750 ended much differently than it began. Our mildly indifferent reaction to its announcement at the beginning has been altered through getting to know it, to enthusiastic fondness for this superbly conceived and executed motorcycle. The only note of disappointment arose after all the testing and poking and prodding had come to an end, and that was when Yamaha took it back.
