1981 Honda CBX Road Test - page 2

Most of the power-curve reshaping seems to have been accomplished by giving the CBX a new set of camshafts. These close the intake valves five degrees earlier than before, and retard both the opening and closing of the exhaust valves by five degrees. Intake lift is up 0.2-millimeters, to 8.0mm; the exhaust from 7.0mm to 7.5mm. The cams' profiles also have been revised to reduce tappet noise, and the '81 CBX is quieter than first or second editions of Honda's Six even with the fairing beaming noise at its rider's ears.

Subtle exhaust system changes are included in the 1981 CBX package and these, too, are said to nudge midrange power upward. There's an exhaust cross-over just upstream from the bike's twin mufflers, and we are informed that the individual pipes terminate at different lengths inside the collectors. Presumably they have done this so that instead of hitting exhaust resonance together the cylinders come "on the pipe" in pairs at different engine speeds. This, too, spreads power range at the expense of the engine's power peak.

Into the factory phone booth went the CBX, wearing its Superman vestments. Then out it came as a marathon runner dressed in After Six apparel. The ultra-high-performance crowd may be unhappy with the transformation. Others will be delighted: Who liked Superman anyway?
Other engine changes are minor, and made in the interest of refined running and reliability. The 28mm Keihin constant-vacuum carburetors have been remounted slightly nearer horizontal, for a better idle. An oil feed hole has been added in the starter clutch shaft, to allow a tightening of hub clearances for quieter running. The top piston rings' chromium facing has been doubled in thickness from 0.05mm to 0.10mm for greater durability. Oil control has been improved with the switch to narrower oil rings and also by means of a half-degree increase in the taper of the second rings’ faces. All the valve seats are now cut to a 1.0mm width instead of the previous engines' 0.7mm and this, too, is for long-term durability.

No changes in the CBX's transmission have been made-all the ratios are exactly as before-but the shock absorbing medium in the clutch hub is now coil springs. Earlier CBXs had rubber-loaded clutch hubs, which were fine until age and exposure to hot oil converted the rubber from elasticity to malleability. The coil springs probably won't be quite as good as new rubber; they'll be considerably superior to the solidified article.

Honda wanted the revitalized CBX to be the equal of its toughest competitor with respect to handling. It should come as no surprise that Suzuki's GS1100 was selected as the target bike, nor that Honda should resort to modestly heroic measures in an effort to make the CBX as good.

One thing Honda did was to revise the CBX's steering geometry and its fork very extensively. They re-angled the frame's steering head to provide 29.5 degrees of rake, two more than before, and then made up fork bridges with more forward offset to hold the trail at 120mm (4.72 inches). The new bridges also space the fork tubes 10mm farther apart, on centers, which is necessary because the tubes' diameter has been increased to 39mm. We always thought, and said, that the earlier CBX's 35mm fork tubes were too skinny for its weight and overall performance; the new ones aren't.

Previous page     Next page
PAGE: Home Tests 1 2 3 4 5 6 7