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:
- It should ‘take your breath away’ when being driven
- It should be comfortable and manoeuverable
- It should make the rider look good
- It should be safe to ride and not be tiring
- New technology should be applied to make 1 to 4 possible
- It should be purchased for under $1000 (about USD$4,650 in 2017)
Air-cooled CX350 prototype photos:
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:
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:
Note the 22-degree twist appears to be evident, though the rocker cover doesn’t quite look like the production models.
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:
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.