[Webike Vintage Bike Info] SR500 vs. SR400: A Comparative Analysis

Motorcycle

Interview Assistance: Motorcycle King Tsukuba Out of Print Museum

The SR500/400 was launched in 1978, 47 years ago (2025), and the SR series was a road sport model developed based on the engine and frame of the XT500 off-road motorcycle. The Road Bomber, which was built by Shima R&D and equipped with an XT500-based engine, entered the 1977 Suzuka 6-hour endurance race and became the talk of the town.

From the XT500-based road sports to the neo-classic

The SR500/400, developed based on the XT500, was initially developed as a road sports motorcycle with a disc brake on the front, but as it was often used as a base for a classic style custom motorcycle, Yamaha, the manufacturer, made an unusual change to the specifications by changing the front brake to a drum brake for the 1985 model. Another reason for this change was that the single bike SRX600/400, which had a stronger sporty character, was released in the same year, 1985. Yamaha's strategy was to offer the SRX to sports-oriented users and the SR to classic-oriented users.

The XT500, the base of the SR series, features a dry-sump air-cooled single-cylinder engine and an oil tank frame.
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The first-generation 1978 SR500 was a road sport model with disc brakes on the front and a single engine.

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Equipped with a double cradle frame and front and rear disc brakes, the SRX was released in 1985 in two models, the 600 and the 400.

The SRX maintained a certain level of popularity, and in 1990 a new model equipped with an electric starter and 17-inch wheels was released, but this model was not well received by users and production was discontinued after the 1991 model. However, the SR500/400 continued to sell well thanks to the classic bike boom, and production continued with minor changes. The 2001 model of the SR400 was equipped with an A.I.S (Air Induction System) to comply with emission regulations and the front brake was changed to a disc, but the 1999 model was the final model for the SR500.

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With the model change in 1985, the SR series saw its front brakes converted to drum brakes, and the series shifted to a neo-classical style.

The "20th Anniversary" model, which was released in 1998, reproduces the coloring of the first model.
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Even after production of the SR500 was discontinued, the SR400 was revived to comply with emissions regulations and was modified with changes such as changing the front brake to a disc.

Air-cooled single-cylinder engine with displacement adjusted by stroke

As mentioned earlier, the SR500 was initially equipped with disc brakes, but these were replaced by drum brakes at the 1985 model change. The 1985 model change saw the 12-liter fuel tank replaced with a 14-liter one, and the 19-inch front wheel was replaced with an 18-inch one, among other major modifications. Various minor changes were made after that, and the fuel tank was changed to a 12-liter specification again in 1997. The model photographed here is the 20th anniversary model released in 1998, and features the Deep Red Cocktail 2 coloring, which is a reproduction of the original coloring of the model when it was first released. Originally, the side covers would have the “SR500” logo in gold, but this vehicle seems to have been changed to the SR emblem.

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The 1998 model photographed here is the “Deep Red Cocktail 2,” a reissue of the first-generation color with gold lines that enhance the body.

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The rear view, which gives a tight impression, asserts that the SR is originally a sport bike.

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The upper body leans forward lightly, and the step seems more forward than one might expect. It would be good to adjust it to your liking with the countless custom parts available.

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A 171cm tall, 65kg rider sitting astride. The seat is thick, so the rider's heels feel as if they are lightly floating on the ground.

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The cut glass lenses and large round blinkers give the car a retro taste. The screen was retrofitted.

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Twin-light type meter with white panel. Indicators are housed inside the meter for a simple design.

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The classical design and large switches are characteristic of SR. Visible under the grips is a decompression lever to relieve compression.

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The right side switch box, including a kill switch that turns left and right and a sliding hazard lamp switch, is also of classic design.

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A 14-liter fuel tank was installed in this vintage. Gold emblems and stalliping tie the design of the tank together.

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The flat design of the seat is thick and creates a comfortable ride. Its length also makes it suitable for tandem use.

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Compact tail cowl and chrome-finished rear fender combine to form the tail area. The rear carrier is made by Wise Gear.

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The emblem on the side cover seems to have been changed by all owners. Originally, it should have the “SR500” logo.

The XT500 engine on which the SR500 is based has a bore x stroke of 87 x 84 mm, 499 cc, compression ratio of 8.3, maximum output of 30 PS at 5800 rpm, and maximum torque of 3.9 kgm at 5400 rpm. The SR400 has a 399cc engine with a bore x stroke of 87 x 67.2 mm and a compression ratio of 8.5, and maximum output of 27 PS/7000 rpm and maximum torque of 3.0 kgm/6500 rpm. Generally, when changing the displacement based on the same engine, the bore is often adjusted, but in the case of the SR, the displacement was adjusted to the so-called mid-sized displacement by shortening the stroke, and at the same time, the engine was tailored to have a higher rpm.

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The compact, air-cooled, SOHC single-cylinder engine with dry sump system is considered to be kick-start only.

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The 499cc engine has a maximum output of 32PS/6000rpm and a maximum torque of 3.7kgm/5500rpm. The displacement is different from the 400 due to the difference in stroke.

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The carburetor is a Mikuni BST34. This carburetor was adopted from the 1988 model onwards; prior to that, the VM34SS carburetor was used.

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A beautifully plated exhaust system. It is often the first part replaced after purchase, so a normal one may be rare.

The biggest attraction of the SR500 is the torque feeling of the engine that its long stroke produces, and when you compare it to the 400, you will be surprised at the difference in character. Also, while the SR500's specifications have not changed, the early models are equipped with what is commonly known as a "heavy crank," and this heavy crank is popular because it gives a feeling more like a single. I'm sure it has to do with licenses, but if you are thinking of buying an SR, I would recommend that you try riding the 500 and 400 to compare them.

Oil tank frame that created a Slim body

The SR500/400 is based on the XT500, and one of its features is that the oil tank is located in the frame because the engine is a dry sump. Since the XT500 is an off-road model, this oil tank frame was adopted to ensure constant lubrication while gaining ground clearance, and to pursue a slim design that would give it an advantage in terms of maneuverability.

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As the main tube of the frame doubles as the oil tank, an oil filler cap is attached to the neck.

The suspension is extremely basic, with 35mm upright front forks at the front and a steel swingarm and twin shock absorbers at the rear. Spoke-type 18-inch wheels have been used since 1985, and the brakes have also been drum front and rear since this model year. The 1985 model also saw the adoption of fork boots, which add to the classic image, and 1985 was a major turning point for the SR motorcycle.

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The front wheels are 18-inch spoke type starting in 1985. Prior to that, they were 19 inches, and cast wheels also existed.

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The SR is often the base for classic customizations, and the adoption of drum brakes can be said to be a change that reflected user feedback.

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The fork boots, which were adopted at the same time as the drum brakes, were also a part that emphasized the classic look and became a traditional feature of later SR models.

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The rear area features heavy-duty parts such as a steel swing arm and plated chain cover.

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The rear suspension is a twin-shock type, and the plated rear shock is equipped with a preload mechanism.

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The rear drum brake, which was used until the last model of the SR400 with modifications, is one of the traditional parts of the SR.

The change from the original concept of a sport bike to a neo-classic was the biggest factor in the SR becoming a long-selling bike for over 40 years. Fuel injection was introduced in 2010, and production ended in 2017, but it was revived as the 2019 model and continued until the 2021 model year.

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Finally, the SR400 was converted to injection and, after a period of temporary production discontinuation, the Final Edition in 2021 marked the end of its history.

SR500 Main Specifications (1998)

Overall Length x Width x Height: 2085 x 735 x 1080 mm

Wheelbase: 1140mm

Seat Height: 790mm

Vehicle Weight: 170 kg

Engine: Air-cooled 4-stroke SOHC 2-valve single cylinder 499cc

Maximum Output: 32 PS/6000rpm

Max. Torque: 3.7kgm/5500rpm
Transmission: 5-speed return

Fuel Tank Capacity: 12L
Brakes: F=drum, R=drum

Tire: F=3.50-18, R=4.00-18
Price: PHP170265.06 (price at that time including tax)

Photography Cooperation: Bike-Oh Tsukuba Out of Print Museum

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The showroom is stocked with out-of-print cars of all genres. The showroom is stocked with a large number of cars in different colorings, so you are sure to find one to your liking.

Address: 120 Koken, Tsukubamirai-shi, Ibaraki, Japan

Phone: 0297-21-8190

Hours of operation: 10:00-19:00
Closed: Thursday

 

See YAMAHA SR400 Moto Index Page
See YAMAHA SR500 Moto Index Page

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