# Yamaha Motorcycle Quick Shifter

See how a quick shifter lets a rider change up a gear without the clutch: a sensor feels the push, the engine pauses its spark for a split second and the gear slips in

By L\.E\. G\.O\.

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/kqdVxw46DbDD)

## Guide

### 1. A gear change faster than a blink

This is the left side of a sport bike's engine, cut open so you can see inside\. A quick shifter lets the rider change up a gear without touching the clutch\. The whole change takes less time than a blink\. Let's slow it down and watch\.

Drag anywhere to turn the engine around\.

### 2. Gears that lock with chunky teeth

Inside the gearbox, pairs of gears are always turning\. A sliding ring decides which gear actually drives the back wheel\. It locks onto a gear with chunky square teeth called dogs\.

The glowing faces are the dogs pressing on each other while the engine pulls\.

### 3. Why riders usually need the clutch

While the engine is pushing, the dogs are squeezed together hard\. Even a strong push on the gear lever cannot slide the ring free\. Normally the rider pulls the clutch lever to take that squeeze away first\.

### 4. The rider's toe lifts the lever

To change up, the rider lifts the shift lever with their toe\. A thin metal shift rod carries that push up to the shift shaft on the gearbox\. With a quick shifter, this is all the rider does\.

### 5. A sensor that feels the push

Part of the shift rod is a small black sensor\. It has no buttons\. It feels the rod being squeezed, the way a bathroom scale feels your weight, and sends a tiny electrical signal along its wire\.

The orange dot is the signal travelling to the engine's computer\.

### 6. A tiny pause in the spark

The engine's computer, the ECU, gets the signal and skips a few sparks\. For a few hundredths of a second the engine stops pushing\. The throttle stays open and the clutch stays untouched\.

Real cuts usually last somewhere around 15 to 75 thousandths of a second\. Here it is slowed right down\.

### 7. The gear slips in

With the push gone, the dogs stop squeezing\. The shift drum turns, the fork slides the ring across and it locks onto the next gear\. Then the sparks come back and the engine pulls again\.

### 8. Try it yourself

Press Shift up, or tap the rubber toe pad on the lever, to replay a change from 2nd to 3rd gear in slow motion\. Watch the lever, the signal, the spark and the ring in turn\.

### 9. Smooth, quick and still a clutch

Because the power drops for only a moment, the bike keeps pulling smoothly and the rider stays steady\. Yamaha's kit works for shifting up only\. The clutch is still used to pull away, to stop and to change down\.

The quick shifter never moves the gears itself\. The rider's foot still does that\.