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Yamaha TX500
Yamaha TX500
Yamaha TX500
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Yamaha TX500
1976 Yamaha XS500
ManufacturerYamaha
Also calledYamaha XS500
ClassStandard
Engine498 cc (30.4 cu in) DOHC parallel twin
Bore / stroke72.9 mm x 59.6 mm
Compression ratio9.0:1
Top speed180 km/h (110 mph)[1]
Power36 kW (48 bhp) @ 8,500 rpm[2]
Torque32.6 ft⋅lb (44.2 N⋅m) @ 6,500 rpm[2]
Ignition typebattery and coil[1]
Transmission5-speed fully meshed
Frame typeDouble-downtube full-cradle steel
Brakes1x270 mm (10.5 in) disk Front
179 mm (7.06 in) drum Rear[1]
Tires3.25-19-4PR Front
3.50-18-4PR Rear
Rake, trail26.5°/120 mm (4.6 in)
Wheelbase1,400 mm (55.1 in)
DimensionsL: 2,150 mm (84.6 in)
W: 840 mm (32.9 in)
H: 1,130 mm (44.5 in)
Weight185 kg (408 lb)[2] (dry)
Fuel capacity13 L; 2.8 imp gal (3.4 US gal)[2]
Fuel consumption6.7–5.9 L/100 km; 42–48 mpg‑imp (35–40 mpg‑US) (Highway)[2]
RelatedYamaha TX750

The Yamaha TX500 is a two-cylinder standard motorcycle built by Yamaha and sold in 1973 and 1974. In styling, the boxy cylinders and heads resembled the RD350, rather than the XS650, which resembled the British 650 twins. In 1975 the bike was renamed XS500 and then continued to be updated until 1978 when sales ended in the USA. In Europe, the model was available through 1980.

History

[edit]

The TX500 debuted in Tokyo in October 1972.[3] 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 the engine oil caused by the operation of the anti-vibration system.[4] Yamaha attributed the problem to excessive heat build-up in the engine and a lack of machine durability.[5] In the TX500 excessive heat build-up promoted warped valve seats and cracked cylinder heads.[6] Its exhaust ports were re-shaped on later engines to improve heat dissipation.

1973

  • TX500 is introduced. Model code is 371.
  • Fuel tank is rounded.
  • Side covers have imitation air intakes.
  • Brakes are single front disk, rear drum.

1974

  • Designation changed to TX500A.
  • Rear brake wear sender added.

1975

  • Bike is renamed XS500; full name is XS500B. Model code remains 371.
  • Carburetors receive new jets and plunger-style enrichers.
  • Balance tube added to intake manifold.
  • Enlarged balance pipe installed between exhausts.
  • Fork spring preload reduced.

1976

  • Model designation is now XS500C. Model code changes to 1J3.
  • New, more rectangular tank and new side panels.
  • New seat cowling with integrated mudguard.
  • Front fender is mounted without stays. Fender is now body colored.
  • New 38 mm Mikuni carburetors.
  • Cylinder and camboxes are now a single casting.
  • Compression ratio drops from 9.0:1 to 8.5:1
  • Drive cogs change from 17/43 to 16/42.
  • Front fork is now from Showa.
  • Alloy wheels replace spoked wheels.
  • Disk brake replaces rear drum.
  • Front caliper now mounted behind fork.

1977

  • Model designation changes to XS500D.
  • Compression ratio is raised from 8.5:1 to 9.6:1

1978

  • Model designation changes to XS500E.
  • Last year of sales in the USA.

Engine and drivetrain

[edit]

The TX500 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.[7][3] 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.[3] The TX500 was also claimed to be the first motorcycle to use an integrated circuit-based voltage regulator.[8] 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 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.

Chassis and suspension

[edit]

The frame 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.[1] In 1976 the front disk was increased in size to 298 mm (11.7 in), and 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.

Reviews and riding impressions

[edit]

Early reviews of the TX500 complimented the bike's handling, crediting the Omni-phase system with smoothing out the engine's inherent vibration.[2] 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.[3] The transmission got high marks in other tests, but the carburetors were criticized.[9] Other testers found fault with the push-pull throttle cable arrangement, and commented on slack in the drivetrain causing some jerkiness.[10] 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.[11] Reviews of the revised XS500 indicated that the touchy throttle, carburetor issues and transmission lash of the TX500 had been addressed.[12]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Yamaha TX500

View on Grokipedia
from Grokipedia
The Yamaha TX500 is a standard produced by the Japanese manufacturer Yamaha from 1973 to 1974, featuring a 498 cc air-cooled parallel-twin engine with double overhead camshafts (DOHC) and four valves per cylinder, marking Yamaha's first use of this advanced in a midsize four-stroke model. Designed to compete in the burgeoning 500 cc class against rivals like the Honda CB500, it emphasized smooth high-revving performance and refined handling for touring and everyday riding. Development of the TX500 followed Yamaha's successful XS650 and TX750 models, aiming to fill a gap between their two-stroke RD series and larger twins with a vibration-reduced engine incorporating an Omni-phase balancer system. The engine delivered 48 horsepower at 8,500 rpm and 32.6 ft-lb of torque at 6,500 rpm, paired with a five-speed transmission, front disc brake, rear drum brake, and a dry weight of approximately 185 kg (408 lbs). Performance testing from the era noted a top speed of around 98 mph, with strong braking and low vibration above 2,500 rpm, though it suffered from low-end torque limitations and occasional stalling at idle. Despite its technical innovations, the TX500 faced reliability challenges, including persistent head gasket leaks, overheating, and difficult carburetor tuning with its Keihin CV units, which tarnished its reputation and limited sales. Production ended after two years, with the model evolving into the XS500 series in 1975, which addressed some flaws but ultimately saw the line discontinued by 1978 amid shifting market preferences toward larger displacements and sportier designs. Today, the TX500 is regarded as an underappreciated among collectors for its boldness, though its scarcity—due to short production and past issues—makes well-maintained examples highly valued.

History and development

Origins

The Yamaha TX500 made its debut announcement at the Tokyo Motor Show in October 1972, positioned as a supersport intended to rival established European parallel twins such as the . This introduction marked Yamaha's strategic push into the four-stroke market, building on the company's dominance in two-stroke engines to offer a high-performance alternative for riders seeking refined power delivery. The design goals centered on achieving superior performance in the 500cc class through advanced engineering, specifically by adopting a double overhead camshaft (DOHC) configuration with four valves per cylinder, which represented Yamaha's initial foray into sophisticated technology for mass-produced motorcycles. Drawing from the company's racing heritage in two-stroke models like the RD series, the TX500 incorporated stylistic influences such as the boxy cylinder heads reminiscent of the RD350, adapting proven racing-derived aesthetics to a four-stroke platform. Key innovations included the TX500 being the first Yamaha production equipped with a DOHC parallel-twin , which enabled higher revving and compared to contemporary single-overhead-cam designs. To address inherent vibration in parallel twins, engineers introduced the Omni-phase balancer shaft, a chain-driven counterbalancer that effectively reduced oscillations, particularly above 2,500 rpm. Additionally, the model featured an integrated circuit-based , a pioneering electrical component for motorcycles that ensured stable output and reliability in the charging system.

Production history

The Yamaha TX500 was launched in 1973 amid the Japanese motorcycle boom, when manufacturers rapidly expanded four-stroke offerings to capture growing demand in international markets, particularly the . As Yamaha's inaugural production DOHC four-stroke twin, it debuted alongside the larger TX750 sibling model, sharing engineering elements like the innovative while targeting the competitive 500cc segment. Initial sales of the TX500 spanned 1973 and in the and select other markets, with the TX500A variant incorporating minor enhancements such as improved carburetors for better fueling. Following the commercial failure of the TX750, which suffered from reliability problems and tarnished the TX branding, Yamaha renamed the model the XS500 starting in 1975 to align it with the more established XS series. The XS500B of 1975 retained the core design but added refinements like updated jets and a balance tube in the intake manifold. Evolution continued with the 1976 XS500C, which introduced a rear along with angular styling updates including a rectangular ; the 1977 XS500D raised the for improved efficiency; and the 1978 XS500E featured cosmetic tweaks such as new side panels. Discontinuation occurred in the after the 1978 , marking of North American amid ongoing efforts to address early issues like leaks that had hampered market reception. In , production persisted until 1980 to meet lingering demand. The model's abbreviated run, limited to just seven years overall, stemmed from these initial reliability challenges, which curtailed and kept global production volumes relatively low.

Technical features

Engine and drivetrain

The Yamaha TX500 featured a 498 cc air-cooled, four-stroke, DOHC parallel-twin with a 180° and four valves per cylinder, marking Yamaha's first production to incorporate a DOHC four-valve for improved high-rpm . The had a bore and stroke of 72.9 mm × 59.6 mm, a of 9.0:1, and used lubrication with two oil pumps for efficient oil circulation. It produced 35.3 kW (48 PS) at 8,500 rpm and 44.1 N⋅m of at 6,500 rpm, fed by two 32 mm Keihin constant-velocity carburetors. The included a five-speed constant-mesh transmission paired with a wet multi-plate for smooth power delivery, and a #530 for the final drive. The was equipped with an electric starter as standard, supplemented by a kick-start mechanism as backup. A counter-rotating balancer shaft, derived from the engine's parallel-twin origins, helped mitigate vibrations.

Frame, suspension, and brakes

The Yamaha TX500 featured a full cradle frame constructed from tubular steel pipes in a duplex configuration, which contributed to its structural integrity. This double cradle design fully enclosed the for enhanced stability. The front suspension utilized a conventional with Kayaba units, while the rear employed a with dual shock absorbers that included preload adjustment for varying load conditions. Braking was handled by a single hydraulic disc on the front wheel, measuring 270 in diameter and clamped by a caliper, paired with a 179 single-leading-shoe on the rear. No (ABS) was available on any model. The rolled on spoked wheels, with a 19-inch front rim and an 18-inch rear, fitted with 3.25-19 tires upfront and 3.50-18 tires at the rear for balanced contact. The overall geometry included a of 1,400 , promoting a stable riding posture.

Riding characteristics

Performance and handling

The Yamaha TX500 offered competent straight-line performance for a mid-1970s 500cc twin, with a top speed of around 158 km/h (98 mph) in period tests. Acceleration was brisk by contemporary standards, reflecting the engine's effective power delivery through its five-speed transmission. Handling characteristics emphasized neutrality and stability, thanks to a low center of gravity and overall balance. This setup enabled predictable cornering and agile responses on twisty roads, where the bike maintained composure without excessive lean or wallow, despite its 207 kg (456 lbs) wet weight; period reviews noted handling similar to the lighter RD350 but with added stability. Fuel economy proved efficient for touring, averaging 45-50 (5.2-5.9 /100 km) during steady cruising. Braking performance was adequate and strong for the era, supported by the front disc and rear setup. Overall, these traits made the TX500 a versatile performer for both urban and use.

Reliability and maintenance

The Yamaha TX500, while innovative in its DOHC , exhibited several reliability concerns stemming from its complex engineering, particularly in the engine and related systems. Engine overheating was a notable issue in early models, with temperatures reaching up to 300 degrees during operation, leading to warped heads, leaking gaskets, and in severe cases, cracks between the spark plug holes and exhaust valve seats or even valve seats falling out. Oil leaks were common around the and rocker covers due to these thermal stresses and the two-piece head construction, contributing to the model's reputation as less reliable for long-term use. Despite the inclusion of an Omni-Phase balancer shaft to mitigate vibrations, some owners reported persistent loosening of accessories and a characteristic whine from the balancer at around 5,000 rpm, necessitating frequent checks and tightening. Drivetrain components also presented challenges, including premature slack in the primary chain and balance shaft chain, which could lead to accelerated wear on sprockets if not addressed promptly; the long and complicated cam chain routing further required consistent tensioner adjustments to prevent jumping or failure. Carburetor synchronization proved difficult with the stock Keihin CV units, often resulting in uneven power delivery, rough idling, and stalling at low speeds or traffic lights due to poor throttle response and mixture inconsistencies. Routine maintenance for the TX500 was more demanding than contemporaries owing to its DOHC valvetrain complexity, with valve clearances needing regular inspection and adjustment—early models suffered from overly tight exhaust valve specs that exacerbated overheating and wear. Frequent oil changes were recommended to manage heat buildup in the , alongside periodic replacement of the element to maintain integrity. The electrical system, including the IC voltage regulator, was prone to failures that could affect charging and starting, requiring checks with a fully charged battery and running to verify output. Balance shaft chain adjustments were specified at 6,000-mile intervals to avoid slippage. Subsequent variants under the XS500 name introduced key improvements to address these flaws, such as a one-piece and cam box for better sealing and reduced leaks, enhanced cooling fins, upgraded oil seals, heavier flywheels for smoother operation, Mikuni carburetors for improved synchronization, and lower compression ratios to mitigate overheating. The XS500 continued production until 1978 in the and 1980 in .

Reception

Contemporary reviews

Contemporary reviews of the Yamaha TX500, introduced in , generally praised its braking and handling capabilities for a . The front was lauded as "superlative" for its strong, fade-free performance during panic stops from 60 mph, while the rear drum provided reliable stopping power. Handling was commended for its similarity to the lighter RD350, offering stability on winding roads with a comfortable riding position from low handlebars and well-placed footpegs, though softer rear springs led to some wallowing in fast corners. The electric starter was a highlight, firing the quickly and allowing it to settle into a smooth idle with minimal noise. Styling drew positive notes for its modern, RD350-like appearance, featuring boxy cylinders, integrated engine castings, and high-quality finishes in , , or black paint with ample chrome. Power delivery was smooth and responsive, with the Omni-phase balancer effectively minimizing up to the 9,000 rpm , earning praise for its refined four-stroke character in the 500cc class. Cycle World highlighted the 's strong while acknowledging the overall low levels. Critics pointed to a touchy response from the push-pull cable setup and slack caused by cushioning springs, resulting in jerky low-speed control and clunking during shifts despite the close-ratio five-speed transmission's light action. Priced at $1,350, the TX500 was viewed as offering good value as a feature-packed newcomer, though reviewers warned of early issues like the imprecise low-rpm . Rider impressions emphasized its docile manners at low speeds contrasted with lively mid-range pull, positioning it as a capable alternative to rivals like the Honda CB500 in performance, but some found its finish quality less polished than British options such as the Triumph T100R. In a direct comparison, the TX500's superior features positioned it ahead of the lighter T100R, though the Triumph held an edge in character.

Legacy and modern assessments

The Yamaha TX500's brief production span of just two years (1973–1974) has endowed it with considerable rarity, limiting availability and elevating its status among vintage motorcycle collectors who appreciate its role as Yamaha's inaugural midsize four-stroke model. This scarcity stems from modest sales figures, overshadowed by competitors like the Honda CB500 and Yamaha's own two-stroke RD350, which ultimately curtailed its market penetration. The model's technical innovations, including its DOHC eight-valve parallel-twin engine and Omni-phase balance shaft, marked a significant evolution in Yamaha's engineering, paving the way for the improved XS500 successor and broader adoption of DOHC configurations in later motorcycles like the XS1100. In contemporary enthusiast circles, the TX500 is regarded as a pioneering yet flawed artifact of Japanese , often dubbed a "troubled " for its reputation as an undeserved "" due to early reliability woes such as leaks and overheating. Modern evaluations highlight its collector appeal for the advanced features that anticipated four-stroke dominance in the 500cc class, though restoration remains challenging amid parts scarcity—particularly for mufflers, cylinder heads, and Keihin CV carburetors—necessitating creative sourcing or aftermarket alternatives. Enthusiasts frequently discuss modifications like electronic ignition upgrades in forums to mitigate original shortcomings, enhancing rideability while preserving its smooth, rev-happy character in restored condition. In the vintage market as of 2024, sales data for unrestored original TX500s range from around $2,000 to $6,000 depending on condition and mileage, while fully restored examples or those with low miles can command $10,000 or more, reflecting growing interest in its historical significance.
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