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In Search of the 11 Second CBX - page 4 |
Going back to the original 469 specs showed us what the difference was, back-to-back, between that unit and the 469A. At peak output, the difference was 5.62 horsepower (82.83 versus 77.21), and that matched coincidentally the 5.62 horsepower-spread at peak between the 1980 engine with the 469 advancer run on a hot day (71.59) and a cooler one (77.21). Half the 11.24-horsepower pick-up came from the cooler day, half from the 469A advancer.
As of November 15, 1979, the loose ends were tied up. First, Honda had its 11-second CBX. Second, we knew how they got it. Third, we could explain any anomalies in the dyno figures. Fourth, the EPA had notified American Honda that the "running change" had been accepted, and therefore the customers could get the 11-second fix.
Only one snag remained. Not one of the machines destined for customers had been changed. And none would be changed before leaving Honda's warehouses, beginning in late December 1979.
American Honda had the option of doing a warehouse retro-fit or a dealer-installed switch. A warehouse number would guarantee that 100 per cent of the machines would be modified. Dealer programs are less than 100 per cent effective because some dealers will neglect to do changes unless the customer insists on the corrective action. A Service Bulletin from American Honda, entitled "1980 CBX Ignition Timing Advancer," dated December 1979, covers the change.
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The 469 part comes out; the 469A part goes in. It is a warranty procedure that affects engine numbers SCO3E-2000001-2001773. All machines with this engine number range fall within the frame number range SCOE-2000001-2001785. [Preceding should read: engine #s SC03E-2000001 to 2001773, frame #s SC03-2000001 to 2001785 --DJH]
Mechanical advance systems utilize flyweights which by means of fingers engage either a breaker-point cam or a trigger unit. As engine speed increases, centrifugal force causes the spinning flyweights to move outward, overpowering small springs. Pivoting on their posts, the flyweights turn the cam or trigger unit which can move independently of the backing plate that holds the flyweights. By varying the weights or springs in this system, the point at which the spark plugs are triggered can be varied.
A simple, single-stage advancer has two weights, set 180 degrees apart on the backing plate, and this type of advancer gives a single, straight advance. The 1980 469 advancer is this type. It provides one degree of advance at 1200 to 1400 rpm, about 10 degrees at 2000 rpm, and 26.5 degrees at 2300 rpm to 23.5 degrees at 2500 rpm. Note that these specs aren't exact; they establish a range in which the ignition curve of any one bike should fall. That's as close as manufacturing tolerances can hold the curve.
More importantly, when the single-stage advancer reaches its peak advance, 2300 to 2500 rpm, that's it. But the ignition timing isn't 25 degrees at 2400 rpm, for example. It's actually 35 degrees, because the CBX uses 10 degrees static advance. There's also an electronic device in the CBX's ignition-timing act. It gradually backs the timing down, starting at 2300 to 2500 rpm, so that at 8000 rpm the timing is about 31 degrees (10 from the static setting, plus 25 degrees from the mechanical advancer, minus four degrees taken out electronically).
The CBX engine likes more advance than this. The 1980 469A advancer is a dual stage unit. The flyweight on one side of the mechanical advancer is actually two separate weights, each with its own engaging finger. These Bobbsey-twin flyweights share the same post; the second weight comes into play at a higher rpm-level than the first; hence, a dual-stage system.
In practice, the 469A advancer bumps the ignition timing a second time, picking it up from 24. 5 degrees at 5200 / 21.5 degrees at 6400 rpm, then lifting it up to 34 degrees at 5600 rpm / 31 degrees at 7000 rpm. That's the range. Add in the 10 degrees static advance, and you're looking at an engine that could be running 41 degrees full advance at 8000 rpm rather than 31 degrees. The 469A second stage, then, accounts for 10 degrees more advance after about 6000 rpm. The CBX's electronics gradually retard the ignition from its high point in the 5600-to-7000 rpm range; the only difference is that the retarding process works against a much higher advance base with the 469A system.
The 469A actually advances the ignition a little sooner than the 1979 422 system; that was primarily necessary to make it compatible with the 1980 CBX's cam timing, and to a lesser extent, the 1980 carburetion.
This episode makes three things clear. First, Honda in Japan was prepared to take remedial action when Cycle discovered the 1980 CBX was not an 11-second motorcycle. No one at American Honda wanted to flimflam us, or even considered it, to the best of our knowledge. A tweaked 1980 CBX might have been an 11-second magazine bike, but the paying customers would shortly find that their six-shooters weren't. Besides, had this magazine been given a ringer - and found the plot out - someone in Gardena would have gotten roasted. True, the GS1100ET Suzuki is so much quicker than the CBX that to some individuals it doesn't much matter whether the CBX is an 11-second motorcycle. Furthermore, the 1980 CBX is sufficiently complete as a motorcycle that three-tenths in the quarter-mile may hardly seem worth the bother. But to Honda those things were important. American Honda wanted the record straight, and the company was willing to provide detailed information for that record.
Another thing is clear. Owners of 1980 CBX Hondas will want to check their motorcycles to insure that the switch in advancers has been made. The numbers 469 and 469A are clearly stamped on the pieces involved. It's a simple, warranty procedure; American Honda believes - and we agree - that making the spark advancer a public issue will generate a broader change-over.
One more thing. We learned a lot more about the CBX than we knew before: about its sensitivity to timing, and to engine heat. And about Honda's commitment to the CBX.
Ironically, had the CBX arrived at the drag strip the first time on a cool day, and had the bike run at the dyno on a cool day; it's conceivable that that bike might have run in the elevens and pumped out about 78 horsepower. Maybe there wouldn't have been a change or a story.
Still, things didn't happen that way. Moreover, until we knew that American Honda had the parts, the EPA approval and a set procedure for the modification, there was no 11-second CBX. Not by our lights, not until late December 1979.
Much as we liked the CBX as a 12.16 motorcycle, we like it better as an 11.86 machine. Because twelve is twelve and eleven is eleven.
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