Honda CX 500 Euro

The CX series motorcycles feature a crankshaft configuration aligned longitudinally with the axis of bike, sometimes called a "flying" V-twin, because the cylinders point up on either side of the motorcycle but are not symmetrical.

The CX was the first V-twin motorcycle that Honda ever built. Honda built a prototype CX350 but it was never released to the public. In that version the cylinders did not have the characteristic 22 degree twist. Initially conceived as having a full 90 degree angle between the cylinders like the similar Italian Moto Guzzi machines, early testers reported that the prototypes were too smooth. Also, the carburetors, which projected directly rearward from the cylinders, tended to interfere with the knees of riders. Subsequent engine designs had their V-angle tightened somewhat to 80 degrees, and the heads twisted inward at the rear by 22 degrees.

An innovative design places the crankshaft above the transmission, with both in the same housing. This keeps the engine short but quite tall.

The engine design combines a 10.0:1 compression ratio and 9,650 rpm redline with overhead valves and a camshaft nestled at the base of the V between the cylinders. There are four overhead valves per cylinder, with unique forked rocker arms acting off each pushrod. The engine runs well on 87 octane petrol. It delivers nearly 50 hp (37 kW) at 9,500 rpm with high low-speed torque characteristics. Moto Guzzi, with their contemporary V50 Monza, delivered 48 hp at 7,600 rpm.

This was from an aircooled, 2-valve 90° V-twin. This Guzzi model is little known outside Europe, so a direct comparison with Honda's CX500 is possible only on paper or amongst motorcycle enthusiasts.

The cylinder bores are cast in the crankcase which complicates the overhaul process although many examples have gone 200,000 miles or more without any major engine work.
Transmission

The transmission spins opposite the engine crank to counteract the engine torque's tendency to tip the bike slightly to one side when the throttle is opened or closed. The gear shift lever is moved with the usual up-down motion of the left foot, but instead of rocking in a forward-backWard motion as on regular bikes, it moves left-right. This difference is transparent to the rider, however, and requires no change in shifting technique. It also means that it is not possible to adjust foot peg and gear lever setup when personalizing riding position.

Power is transferred via an enclosed splined driveshaft with one universal joint. The shaft drives a bevel gear to which the wheel is joined via a cush-drive, which absorbs and dampens driveline shocks and vibrations. The bevel drive spins in an oil bath, and a zerk fitting is provided for greasing the shaft bearing. This reduces the motorcycle's maintenance costs.
Wheels

The original Com-Star wheels combine the flexibility of spoked wheels (without the maintenance burden) with the strength and tubeless characteristics of one-piece wheels. This was one of the first production motorcycles to be equipped with tubeless tires along with the CBX six. Honda introduced the Com-Star wheels a year or so earlier on the CB250T/400T Dream as well as on the CB750F2 and GL1000 Gold Wing, although these featured standard rims that demanded inner tubes to be used.
Chassis

Early versions had conventional suspension, consisting of hydraulically damped telescoping front forks and dual coil-over shocks at the rear. Later versions had air-assisted forks and featured Honda's Pro-Link monoshock rear suspension. US bikes (except GL500I, GL650I and Turbo) were equipped with a single front disk brake whereas all other bike possess dual front disk brakes. Models after 1980 sport dual piston calipers replacing the single piston caliper of the earlier models. For the Turbo and Eurosport models the rear drum was replaced with a dual piston caliper and disk. All models feature steel tube frames with a large backbone, with the engine used as a stressed member. The dual shock models use a single tube backbone whereas the later Pro-Link models employed a triple tube backbone. Later models are blessed with larger front forks and a factory installed fork brace which provides a noticeable improvement in handling.

Introduced in 1982 the EC variant is a much improved motorcycle compared to the original 500. Sharing many parts with the CX500 Turbo introduced the same model year, the Eurosport features air assisted front forks with anti-dive mechanism and air assisted prolink single shock rear suspension. The wheels are also modified, with an 18-inch-diameter (460 mm) restyled round hole comstar front with a 100–90H18 tyre, whilst on the rear is a 120–80H18 tyre.

The brakes are vastly improved with much more effective twin pot calipers on the front and a new disc brake with twin pot caliper on the rear replacing the original drum. The Eurosport is also significantly restyled with a larger fuel tank, a nose fairing, side panels, seat, and tail unit that share much more modern lines. In the UK only two colour options were made: white metallic with blue and red striping, or black with orange and silver stripes.

The instrumentation is improved with the introduction of a fuel gauge and like the rest of the bike a much updated appearance. Plastic mudguards replace the chromed steel versions on the earlier machines curing the associated rust problems. The round headlight of the early bikes is also replaced with a rectangular lens which gives improved night lighting.

The changes extended to the engine where Honda's early 1980s issues with cam chains were dealt with via the introduction of an automatic tensioner replacing the manual version on the earlier models. Other changes also meant that the standard valve clearances were reduced, possibly through tighter manufacturing control. Eurosport model engines are identifiable via the lack of a cam chain tensioner bolt and the revised valve covers which feature black painted stripes and satin alloy flat areas.

The changes made the 500 Eurosport significantly better to both look at and ride, and more reliable than the previous versions. The later CX650ED shared the majority of the cosmetic changes introduced by the 500EC, whilst in Japan a 400 cc version was introduced with the same styling to comply with licence rules.