Background on the CX500
By: Eirik Skjeveland (Eirik.Skjeveland@Bedrift.telenor.no)
I'm indebted to Eirik
Skjeveland who corrected some inaccuracies in my orginial posting (i.e., the
500 Turbo was not developed for the racing circuit). He has graciously allowed
me to edit and share his messages.
Honda did not develop a 500 cc pushrod twin for racing. They did
development work on a turbo, a 250 cc with oval pistons. In fact, it was more
or less 1/2 of a NR 500 engine. The reason for only 250 cc capacity was that
FIM will not allow more for supercharged bikes. Problem was, as You mentioned,
a trouble in controlling the power, although it did produce 150 hp so it was
The development of the CX based 500 cc Turbo and the NR based 250 cc
Turbo was done by completely different teams. The race version was an effort by
HRC (Honda Racing Corp.), the CX by Honda`s ordinary motorcycle engineering
team. The CX started as a "show off" effort. Honda wanted to flex it muscles,
saying to the whole world "look what we can do!". In this respect, the project
was very similar to the later NR 750.
Honda learned a lot from this bike, most of all how not to make a Turbo.
A very low compression (7.2:1) combined with high turbo pressure (19.1 PSI),
produced a nearly unridable bike for normal conditions. Power delay was normally
2 sec. from normal cruising speeds, and then it all came in with a bang. Off
boost any old bike with more than 100 cc would out-accelerate the Turbo from a
standing start. When gas flow was high enough to get the turbo spinning, usually
between 4-5000 rpm under full throttle, you had to be careful not to run over
any car in front of you. Overtaking demanded a curious technique - pin the
throttle and drag the brakes until no oncoming traffic was in sight, release the
brakes and BOOM you passed the startled car driver. Because the torque is very
even on boost over the rpm range, gear selection becomes non critical. From 100
kph (60 mph), the little 500, which was heavy as an 1100, would stay with a 1100
in roll-on contests.
Since the peculiar power delivery of the 500 was more than most could
handle on tight, curvy roads, Honda decided to make a better Turbo;the CX 650 T.
It had, obviously, more displacement (673 cc vs. 496 cc), a higher compression
(7.8:1) and a bit less turbo pressure (17.4 PSI, if my mind serves me
correctly). This bike was a bit easier to ride, but not by much, because it was
so powerful. In 5th gear roll ons, it went from 100-140 kph (62-87 mph) in just
4 sec! A top speed around 140 mph combined with suspension more suitable for a
Gold Wing, made for an interesting ride. As with the 500 before it, the 650 was
no success and disappeared after one year of production.
The engine on which the CX 500 was based, was originally developed for
a small car. Strangely, the first model run produced much more power than the
later ones. Top speed of as much as 116 mph (187 km/h) was reached in tests,
and 0-62 mph (0-100 km/h) as quick as 5.4 sec. More normal performance level is
just short of 110 mph (175 km/h) and 7 sec. The fastest CX I have tried, was my
own - it would lift its front wheel on power only riding two up.
In Europe, the CX family all had twin front discs. A later model, the
EuroSport, also featured a rear disc brake, Turbo styling and Pro-Link, but with
only bikini fairing . The strong point in this little bike is the engine. Many
people experience 100,000 mi. without any problem. Power is scarce, but
delivered evenly over the rpm range, particularly the European versions.
In the end, the CX Turbo resulted in 220 new patents for Honda, witch, I
think, must be an absolute record for one bike. Among others, anti-dive, turbo,
"intelligent" fuel injection, street version of single shock suspension,
twin-piston brake calipers and integrated fairing was all a first for Honda.
None of this was unique in itself, and everything had more or less been seen
before in similar configuration, but never before had so many niceties been seen
put together on just one bike.
Unfortunately, Honda decided to drop the whole CX line in the end of
1983. In Germany alone, Honda sold more than 40,000 CX`s, and still they fetch
abnormally high prices (the 500 is actually more expensive than the 650 there).
In Norway, were I live, the CX has a very loyal following, although prices are
not particularly high. But I cry when I see what some of you paid for your
bikes. A friend just got a US spec SilverWing 500 from USA (they never came to
Norway) without fairing, but with saddlebags and topcase. He paid NOK 55.000 for
it (eq. to US$ 8.500)!!! It runs far to lean, and performance suffers as a
result. An ordinary CX in good running condition cost about half of that, a
scruffy bike can go as low as 1/4.