By: Eirik
Skjeveland (Eirik.Skjeveland@Bedrift.telenor.no)
Honda tried a lot of different engine sizes from 600 to 800 cc before settling
on the final 673 cc version. The reasons for making it "only" a 650
was several; it was the best compromise between complexity, cost and power, the
engine and bike could be made lighter than a full 750 and the competition all
made 650s. Kawasaki KZ 650s, Yamaha XJ 650s and Suzuki GS 650s all sold well
enough to encourage Honda to enter. All of the competition made 4 cyl. inline
engines, making the Honda stand out.
Many were disappointed when Honda released the 650 - they wanted a full 750
capacity. "Just ride it" was Honda's reply. Few did, especially the
magazines were reluctant. But when they finally got around to testing it, they
found the engine to be much better than anticipated. It pulled like a full 750
from low revs, and although it didn't have as much top-end power as a well-tuned
bigger engine, it performed flawlessly where most people rode - in the midrange.
To make the 500 become a 650, Honda changed almost every part on the bike. The
crank got big'er journals, the gearbox was made of stronger material, the clutch
was reinforced and so on. Curiously enough, Honda decided to put smaller carbs
on the larger engine, down 1 mm to 34. This was done to help the engine produce
more power in the low- and midrange. Compression was dropped a tiny bit, from
10:1 to 9.8:1, but that didn't make much difference. The camshaft had much more
lift and a bit more duration, and the end effect was a claimed 64 hp @ 8,000 rpm.
The old 500 had 50 hp @ 9,000 rpm. Both figures are from Europe - the American
way of measuring power meant that the rating was 2 or 3 hp lower. The actual
performance was the same, though. The 650 could cover the 1/4 mi. in about 13
sec., one sec. quicker than the 500.
Honda made 5 versions of the 650; GL 650 and GL 650 Interstate - both standing
out from the competition in being pure touring bikes, the CX 650 C - competing
against the KZ 650 SR, GS 650 L and XJ 650 Maxim, the CX 650 E - going up
against the KZ 650 C, XJ 650 Seca and the GS 650 G and E. Finally the Turbo
competing with XJ 650 Turbo and XN-85 (GS 650 Turbo).
When going from 500 to 650, Honda took the opportunity to reinforce the chassis
as well. The fork went up from 35 to 37 mm stanchion tubes, the frame was made
from larger tubes and suspension received stronger springs to allow them to
operate with lower air-pressure. This made the suspension more compliant due to
less stiction. About the only parts left over from the 500 was the oil-filter
and drive shaft. The drive shaft was used on the CX/GL 500 & 650, the CB
900/1000 C and GL 1100 - it's that strong!
The 650 never became as popular as the original 500, and Honda decided to drop
it after only one year of production. This, more than anything, has helped the
bike receive a strong following it experience today.