Motorcycles have largely ignored the trend of automatic transmissions, although there have been a couple of noticeable exceptions. Similarly, manufacturers haven’t followed current trends and gone over to twin clutch gear boxes.
The closest we’ve come to these technologies is the quick shifter, now commonplace on sports machinery. Quick shifters basically sense a load on the gear lever and send a signal to the ecu (engine control unit) to back off power for a fraction of a second. This unloads the drive chain, allowing the rider to change gear without the clutch. Upshift quick shifters appeared first, but now many allow up and down shifting.
The same technology also allows auto-blipping, where the engine revs are changed to match the road speed for a lower gear when changing down.
Quick shifters work because motorcycle transmissions are constant mesh, the gears are already meshed or engaged, so there is no crunching as teeth try to engage one another.
Manual transmissions
This means if you are going to ride a motorcycle you are going to need similar skills to driving a car with a manual transmission.
If you are making a machine that converts the output from an engine to movement you need to design a way to disconnect the power from the drive. This allows you to stop the movement without stopping the engine. On most motorcycles this is achieved by using the clutch.
A clutch is basically a high friction disk that can be pushed against the engine so it turns as well. The drive is attached to the clutch and is driven by the engine. When pressure is released from the clutch it no longer turns although the engine still runs.
So, when you pull on the clutch lever it has the effect of reducing pressure on the clutch plate. As you let out the clutch lever, pressure is applied to the clutch plate and the engine’s power is passed through the gear box.
Change gear…
The gear box is used to increase torque while reducing the speed of the engine. This means that the output shaft of a gearbox rotates at a slower rate than the input shaft, and this reduction in speed produces a mechanical advantage, increasing torque. (wikipedia)
In a nutshell, low gears give you more oomph, but the motor will start to rev harder.
This means you will have to change gear. Easy, pull in the gear lever as you roll off the throttle. You have to get the timing right, otherwise you will loose forward momentum or the motor will bounce of the rev limiter without going anywhere.
Put your toe under the gear lever and firmly lift the gear lever up (unless you have an upside down shift, of course, but if so you probably don’t need to be told how to change gear).
Let the clutch lever out while rolling on the throttle. Again, timing is the key.
As you slow down, you will also need to change gear, but this time to a lower gear.
The key to a smooth down change is to try to match engine revs with the new gear. Because it is a lower gear, the engine will need to rev faster for the same road speed. Truck drivers do something similar, called double declutching, but they have a neutral between each gear. We don’t, so we only have one clutch engagement/ disengagement but we can still give the motor a rev mid change so when we let the clutch lever out the motor is doing the right revolutions.
Many sports bike use a slipper clutch, so if you don’t get it right you will not lock up the back wheel because the engine speed does not match road speed.
Remember the quick shifter for up changes?
You can also get faster changes without a quick shifter, at least while changing up. All you need to do is unload the transmission while having an upward load on the gear lever. Drag racers used to thumb the kill switch, but if you try that on a road bike it will not release as you remove pressure, so you’re going to drag (no pun intended) to a stop. Rather, just back off the throttle slightly. You’ll get a fast up change.
Down changes, unfortunately, have to be old school with the clutch. But, given the satisfaction of rev matching with a throttle blip, there’s nothing wrong with that!