CMS-Japanese Motorcycle Supply Parts


Honda CX350 and CX360 prototypes for the Honda CX500, GL500, CX650, GL650, Turbos


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As mentioned on the main history page, it is said that the Honda CX500's roots belong in the mid-70s with a pair of prototypes - firstly, the CX350/A3/A23 V-twin of 358cc capacity that featured chain drive, an automatic transmission, a 90 degree cylinder angle and was air cooled. The second variant - CX360/A3S - was water-cooled, apparently 80° & and some variants had forced induction. Bore/stroke for the non-forced-induction model was 72x44mm and fuelling was done by dual CV carburetors, eking out 38.3HP at 10,000rpm with a dry weight of 151kg.

There were supposedly set criteria for the prototypes, the goal of which was to produce a basic bike for the 1980s:

Air-cooled CX350 prototype photos:

Here are some photos of the prototypes made for the Honda CX500 range - a CX350 and CX360.

The frame of the above bike is said to be that of a CB200 with modifications. In both of the example models above the engine does not appear to be a stressed member as is the case with the production CX and GL V-twin motorcycles.

The CX360:

Here's a photo of the Honda CX360 - a prototype which led to the Honda CX500.

No cylinder head twist evident there! The wheels are clearly a departure from the spoked wheel designs that were common at the time.

The conclusion was that the prototypes would benefit from a displacement bump and 500cc was settled upon, with a bore/stroke of 78x52mm. The water cooling and shaft drive were retained but the single sided swingarm, single shock at rear, inboard rear disc and leading-axle front suspension were not.

A supposed supercharged CX360 variant ended up only making an additional 5hp (to 43hp) at 8500rpm. The compression ratio had been reduced to 8.7:1 (down from 10.7:1) but the machine weighed an additional 10 kg. The supercharger was a single-screw compressor that was driven off the crankshaft, drawing through a single CV carb.

An interesting bit of history here - in the late 60s a motorcycle company in Japan went out of business and some of the engineers came to work for Soichiro Honda. The company - which started out as Marusho Motor Co and was apparently renamed Lilac Co Ltd in 1863 - was started by Masashi Itō, who had previously apprenticed under Mr. Honda. Some of Marusho's models were sideways 66° V-twins with shaft drive, overhead valves, electric start, telescopic forks and a rear swingarm... sound familiar? You can find some pics of those bikes on this external site.

Some pics of a closer-to-production model:

Here's a photo of the closer-to-production prototypes for the Honda CX500 and GL500 series.

Note the 22-degree twist appears to be evident, though the rocker cover doesn't quite look like the production models.

Here's a photo of the closer-to-production prototypes for the Honda CX500 and GL500 series.

Note the GL500 number plate on the back - this seems to be the JDM (Japanese Domestic Market) designator for the CX line. Some literature for this:

Here's a photo of a brochure for the closer-to-production prototypes for the Honda CX500 and GL500 series.

Here's a photo of a brochure for the closer-to-production prototypes for the Honda CX500 and GL500 series.

Here's a photo of a brochure for the closer-to-production prototypes for the Honda CX500 and GL500 series.

Here's a photo of a brochure for the closer-to-production prototypes for the Honda CX500 and GL500 series.

Anyone able to interpret any or all of the Japanese text? Let us know if you can...

Now head back to main CX/GL history page.



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