| Okay, picture this: You're riding your scooter, accelerating from a light. You shift from 2nd to 3rd, engage the clutch, and twist the throttle all the way down. At first, acceleration is slow, but as the engine's RPMs increase you begin to feel the heat. You notice that as the engine reaches a certain speed, it's power increases and you accelerate at a greater rate. This is because your engine has reached its "powerband." It's like the sweet spot on a tennis racket, the place where you always want to hit the ball. Every scooter is unique, because of differing variables: cylinder size (displacement), carburetion, exhaust, gearing, fuel/oil/air mixture, spark, and on and on. But every scooter has its own powerband, the RPM where it can achieve its best power. In racing, you always want to keep the engine within its powerband, for obvious reasons. | |
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The gears which came with your scooter from the factory were selected so that the average rider, using the scooter in a variety of circumstances, would be able to ride with good fuel economy and adequate speed to keep from getting run over by larger vehicles. In racing, these concerns go out the window. Chances are, your engine is putting out a teensy bit more power than it did back then. A tuned or kitted engine will often turn at higher engine speeds than stock engines could hope to survive. Also, on the race track, we're not so much concerned about fuel economy. We rarely pack riders during races, excepting of course the sidecars. So, the whole equation has changed with regard to gearing. The gears and ratios selected by the designers in 1970 may not be appropriate for the track in 2002. |
| Close ratio gearboxes use different combinations
of gears to keep the engine within its powerband throughout the
race. Now, with a close ratio gearbox, when you shift from 2nd to
3rd your engine doesn't drop down to such a low RPM. By
keeping the engine turning within its powerband, its "sweet
spot," you can maintain constant acceleration throughout the
course of the race. Drawbacks? A few. Since your close ratio gearbox reduces the amount of RPM drop between gears, it also reduces the overall span of speed you can ride in the same RPM range. Depending on the final drive ratio, you may find that you can't cruise at 60 anymore, or that you can't take off as easily from a dead stop. Such are the trade-offs. You wanted to race, didn't you? Or did you want to cruise? One set of gears can be a compromise between both worlds, but no set can give you the best performance on the track and on the street. Unless, of course, you're driving a twist-n-go. Gear ratios don't apply when you don't have gears! But that's the topic of another tip, another day. Contact your favorite shop for details and prices. |
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A valuable related resource is the Scooterhelp
gearing page with diagrams, calculators, and explanations of
Vespa and Lambretta gearboxes. |
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Do you know how to tune a scooter? Want to author an article about a particular tip or technique? Space is available to interested persons who wish to contribute information or a short article, in compliance with rules issued in the introduction. |
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