Misplaced Pages

#65934

37-657: The TX500 debuted in Tokyo in October 1972. It arrived in most markets in 1973, along with the larger TX750 . Like Yamaha's earlier XS650 , both the TX500 and TX750 were four-stroke air-cooled twins. While the TX500 and TX750 were released at or near the same time, there were significant differences between their engines. The short production life of the TX500 was due in part to problems with engine leaks and failures. The TX750 experienced similar problems, which were in part attributed to aeration of

74-517: A vehicle , a gaiter or boot is a protective flexible sleeve covering a moving part, intended to keep the part clean. Gaiters are pleated rubber tubes enclosing the front suspension tubes of some motorcycles and mountain bikes with telescopic front forks. Gaiters protect the sliding parts of the front suspension from dirt and water. Similar gaiters to those described above find multiple uses on most vehicles. They are used at both ends of driveshafts , protecting constant-velocity joints from

111-402: A cooler of their own, mounted low in the air-stream. Yamaha recalled the bikes, a first for the industry, and sent techs out to dealerships to install the oil coolers. Problems specific to the balance system also occurred. The chain driving the counterbalance shafts would stretch, resulting in the counterweights being out of phase with the crankshaft and the engine vibrating more severely than

148-593: A hydraulically-damped telescopic fork with 5.9 in (150 mm) of travel and coil springs with a rate of 2.98 lb⋅ft (4.0 N⋅m). There were no gaiters on the 1.4 in (36 mm) standpipes. A vane-type steering damper was fitted. At the rear was a steel swing-arm that rode in plain bearings. Springing and damping were provided by dual shock absorbers and progressively wound coil springs whose rate varied from 9.83–11.5 lb⋅ft (13.3–15.6 N⋅m) and provided 3 in (76 mm) of travel. The rear-shocks were five-way adjustable units. The TX750

185-567: A more restrictive exhaust in the German market, which lowered output power to 51 hp (38.0 kW) and torque to 42.6 lb⋅ft (57.8 N⋅m). Some reviews of the bike report other differences, such as 8.4:1 compression ratios and 32 mm carburetors, but it is not clear whether these were changes for specific markets or running production changes. Yamaha designed the engine with a unique oil-filter located in an unusual location. Replacement filters are difficult to find, and adapters that allow

222-532: A regular twin would. The tight timing tolerances between the two balance shafts caused some reviewers to worry that a slight maladjustment would cause the eccentric weights on the shafts to run into each other. Yamaha's fix in this case was to revert to an external chain adjuster, which required a modified sump. In all 18 engineering change orders, including a deeper sump, were issued for the engine. The extensively modified 1974 TX750A model does not suffer from reliability issues. Despite Yamaha's efforts to solve

259-533: A series of both major and minor mechanical failures and some rider errors only three of the six were running at the end of the race. The highest placed TX750 finished in fifth place. One of the first TX750s to arrive in Europe was ridden to a sixth-place finish by "Texas" Henk Klassen at the 6 Hour event held at the Zandvoort circuit in the summer of 1973. Yamaha Motor Amsterdam contracted Porsche A.G. Research to prepare

296-519: A spring-loaded chain-tensioner to control lash on the chain driving the Omni-Phase balancer, but this was later changed to drive sprockets with a 1 mm offset which controlled chain lash while offering longer chain life and reduced noise. Both kick-start and electric-start were standard. The electric start added a third chain to the engine's internals. The engine did not have a decompressor. The five-speed fully meshed sequential transmission came from

333-479: A tendency to squirm or wobble when pushed into faster corners. Some reviews recorded high oil temperatures even in testing and recommended prospective owners consider adding an external oil cooler. In September 1972 one of the first TX750s exported to Australia was prepared to challenge the One Hour, Twelve Hour and Twenty-four Hour Australian endurance records. A combination of mechanical problems and confusion over

370-401: Is a two-cylinder standard motorcycle built by Yamaha . The bike was released in 1972. Significant reliability problems affected the engines in early bikes. Yamaha made several changes to solve the problems but the bike was withdrawn from most markets after 1974 and production stopped in the home market after 1975. The TX750 had a double-cradle frame of tubular steel. Front suspension was

407-466: Is smoothness beyond belief," and "Shut your eyes and you are on a four. It couldn’t be a twin." Cycle magazine's issue of March 1973 called the TX750's engine the "Most advanced two-cylinder engine in motorcycling" The controls and instruments were described as top quality and easy to use. The three warning light system drew mixed reviews, with some expressing appreciation for the extra redundancy built into

SECTION 10

#1732891285066

444-565: The 2-into-2 exhaust system were dual up-swept pipes with megaphone ends. The engine used automotive-style plain bearings for the major rotating components. Three bearings were used for the crankshaft and two for the camshaft. The choice of bearings necessitated the use of a high-pressure lubrication system, which in the TX750 was a dry-sump system with two Eaton-type trochoidal pumps; one for pressure and one for scavenge. Yamaha claimed 63 hp (47.0 kW) @ 7500 rpm and 50.6 lb⋅ft (7.0 kg⋅m) @ 6000 rpm. The engine had

481-574: The TX750 to be entered in endurance racing events in 1974. Two bikes were run in the Bol d'Or 24 at Le Mans. The Porsche-prepared engines were replaced with Yamaha engines but both bikes failed during the night with snapped cam chains. The bikes also ran at the Thruxton 500 Miles in England. Both TX750 Endurance racers are reported to have been destroyed after their racing careers were over. Gaiter (vehicle) On

518-610: The XS650 XS1 in 1970. This bike was powered by a Hosk-derived four-stroke air-cooled twin of 654 cc. Work began on a successor to the XS650 two years before its 1972 debut. Although superficially similar to the XS650, the TX750 was an almost entirely new design. The TX750 was featured in an article in Yamaha News magazine in October 1972, and appeared on Yamaha's stand at the 19th Tokyo Motor Show one month later. The standard road bike

555-402: The earlier XS650. The sprocket sizes were 17 front, 40 rear, connected by a #530 chain. The TX750 instrument package included four lamps that warned of various problems. The upper lamp would light whenever the main headlamp was burnt out, while also sending power to a secondary filament. Below this was a lamp that came on when the thickness of the rear brake shoe fell below a specific amount. To

592-412: The engine oil caused by the operation of the anti-vibration system. Yamaha attributed the problem to excessive heat build-up in the engine and a lack of machine durability. In the TX500 excessive heat build-up promoted warped valve seats and cracked cylinder heads. Its exhaust ports were re-shaped on later engines to improve heat dissipation. 1973 1974 1975 1976 1977 1978 The TX500

629-404: The engine's inherent vibration. The brakes were also highly rated. A problem with sticking carburetor slides was experienced. Other reviewers found that power came on strongly and suddenly, especially in lower gears. There was also strong engine braking when the throttle was backed off. The transmission got high marks in other tests, but the carburetors were criticized. Other testers found fault with

666-434: The engine, while the balancer in the TX500 was a simpler version with just a single balance shaft. The chain driving the balance shaft was hidden behind the alternator, making manual adjustment difficult. The transmission was a 5-speed fully meshed unit that drove the rear wheel through a #530 chain and a 17/43 sprocket set. The drive cogs were later changed to 16/42. The bike came with both kick and electric start. The frame

703-413: The existing records caused the attempt to be stopped after six hours. The team claimed the previously unrecorded Six Hour record after having covered 370.23 mi (595.8 km) at an average speed of 61.68 mph (99.3 km/h). The same TX750 was part of a team that appeared at the 1972 Castrol Six Hour race at Amaroo Park . Yamaha put together a six-bike, twelve-rider team for the event. After

740-430: The failures was the oddly shaped and located oil filter. Others blamed the bike's complicated oil system for starving parts of lubrication. Others blamed the quality of the oil available at the time. One of the two most commonly suspected causes was excessive heat coming from the balance tube connecting the exhaust ports. The other most common claim was that the Omni-Phase balancer's weighted shafts were whipping oil in

777-440: The first motorcycle to use an integrated circuit -based voltage regulator. The air/fuel mixture was delivered by two 32 mm Keihin constant-velocity (CV) carburetors in early models and by 38 mm Mikunis beginning in 1976. The TX500 and TX750 twins both featured a vibration control technology that Yamaha called an "Omni-phase balancer". In the TX750 two chain-driven shafts with bobweights counteracted vibrations generated in

SECTION 20

#1732891285066

814-453: The inclined axis of the piston bores. A second shaft with weights rotating in the same direction as the crankshaft counteracted the force couple created by the difference in the vertical height of the fore-and-aft forces created by the crankshaft and the first balance shaft. The Omni-Phase balance system consumed some engine power to operate. In early production models sold in Japan, Yamaha used

851-400: The ingress of dirt, and retaining the grease. They also prevent the ingress of dirt where one component slides within another, for example, on suspension struts or the ends of steering racks. Finally, they are also usually used to perform the same function on ball joints , which appear on suspension wishbones and steering tie rod ends. The gear stick gaiter is to resist dirt entering

888-548: The left of that lamp was an oil pressure warning light, and on the right a lamp that would glow solid red whenever the brakes were applied, and would blink red if the rear lamp was burnt out. Until the early 1970s Yamaha focused on two-stroke bikes, but concerns about pollution had begun to make two-strokes increasingly unpopular. Around this same time competitors started to release new four-stroke multi-cylinder bikes with larger engines and greater levels of comfort. Yamaha added four-stroke engines to their line-up when they released

925-437: The lighting system and others voicing annoyance at the way the warning system operated, lighting a red lamp under normal conditions and flashing in the event of a problem. The bike was characterized as a low-rpm tourer rather than a high-revving sports-bike. The bike's throttle-response and low-end torque were ranked high. In a March 1973 article Cycle magazine called the TX750 "one of the ten fastest production motorcycles in

962-494: The problems, sales of the TX750 never recovered. In general reviewers praised the effectiveness of the Omni-Phase balancer system. A June 1973 review by Big Bike magazine said that at low rpms the TX750 vibrated as much as a typical British twin, but that at higher engine speeds the bike became smoother. Popular Science reviewer Ray Hill called the TX750 "one of the smoothest-riding bikes I've ever been aboard." Cycle World magazine wrote in their October 1972 issue: "The result

999-456: The push-pull throttle cable arrangement, and commented on slack in the drivetrain causing some jerkiness. The bike was described as being heavy for its displacement but not feeling the weight on the road. Some wheel skip was induced on a high-speed decreasing-radius downhill turn. Reviews of the revised XS500 indicated that the touchy throttle, carburetor issues and transmission lash of the TX500 had been addressed. Yamaha TX750 The TX750

1036-467: The rear drum was converted to a single 267 mm (10.5 in) disk. 1976 was also the year that alloy wheels were substituted for the traditional wire spokes previously mounted. The front tire size was 3.25-19-4PR and the rear was 3.50-18-4PR. Rear tire size rose to 4.00H-18-4PR on later bikes. Early reviews of the TX500 complimented the bike's handling, crediting the Omni-phase system with smoothing out

1073-462: The sump into a froth at high rpms, aerating the oil and starving the crank of lubrication which then resulted in bearing failure. Yamaha described the cause as "a problem with heat build-up that prevented stable engine performance and insufficient machine durability". One ready solution was to add an external oil cooler. Coolers from a variety of sources were retrofitted to the bikes, often mounted high and out of sight. Eventually Yamaha came out with

1110-414: The use of more commonly available filters have appeared in the aftermarket. To counteract the vibration that occurs naturally in a parallel twin, Yamaha introduced a system they called the "Omni-Phase balancer". The Omni-Phase system used one chain-driven weighted shaft in the engine sump rotating in the direction opposite that of the crankshaft to counteract forces created by the pistons moving up and down

1147-421: The world" based on its quarter-mile speed. Testers reported noticeable driveline lash, and clunking and lurching when shifting out of neutral. Other complaints focused on a lack of preload in the front suspension, and excessive softness in the suspension and seat pad in general. Handling was described as adequate, with some reviews describing the bike as stable on the straights and in corners, and others reporting

Yamaha TX500 - Misplaced Pages Continue

1184-457: Was a 7.1 in (180 mm) drum with an internally expanding single leading shoe. The front wheel mounted a 3.50 - 19 - 4PR tire while a 4.00 - 18 - 4PR tire was on the rear. The bodywork was finished with a metal-flake paint. Unlike Yamaha's earlier vertical XS650 , the TX750's engine was a forward inclined air-cooled parallel twin with a 360° crankshaft, a chain-driven single overhead cam , and two valves per cylinder. The engine

1221-425: Was a steel double-downtube cradle. The front suspension was a telescopic fork from Kayaba until 1976, when it became a Showa part. Rear suspension was by dual shock-absorbers and swing arm with adjustable pre-load. On early bikes the front brake was a single 270 mm (10.5 in) disk, while in back was a 179 mm (7.06 in) drum. In 1976 the front disk was increased in size to 298 mm (11.7 in), and

1258-419: Was aluminum with a horizontally split crankcase and steel liners in the cylinder bores. The intake system was fed by two 38 mm Mikuni Solex carburetors. New features in this engine included a positive crankcase ventilation system, hardened valve seats suitable for unleaded fuel and a balance tube in a cast manifold that connected the two exhaust ports together on the front of the engine. The balance of

1295-539: Was model number 341, while the police version was model number 435. The police version came with a distinctive valve-cover. The bike was released in Japan in July 1972, and towards the end of the same year in the United States, where it retailed for a price of US$ 1554.00. Shortly after being launched in Europe reports of engine failures began to come in. Several causes for the failures were suggested. One suggested cause for

1332-417: Was powered by a transverse air-cooled parallel twin engine which had a 180° crankshaft. In contrast to the dry-sumped TX750, the TX500 had a wet sump. The valvetrain used double overhead camshafts (DOHC) and four valves per cylinder , which were operated by rocker arms for each pair of valves. Yamaha claimed this was the world's first mass-produced four-valve motorcycle engine. The TX500 was also claimed to be

1369-402: Was the first Yamaha road bike to have aluminum wheel rims. The rims were copies of Akront valanced rims made by DID. In Europe the TX750 had dual front disc brakes with dual expanding pistons on 11.8 in (300 mm) discs. In Japan, the United States, and other markets the bike had a single disc, although the lugs needed to mount a second disc were in place. On all bikes the rear brake

#65934