Ever wonder how a kickstarter works? Jim is here to tell us everything
If you are riding a modern motorcycle, it is probably not equipped with a kickstarter. With the push of a button, your motorcycle comes to life without you having to exert an ounce of effort. Back in my day, when we still had to walk 10 miles to school uphill in the snow (both ways), motorcycles could only be started by frantically kicking a small pedal and all old riders were limping from some variety of jump-related injuries . . For all the young riders who walk without any constant knee pain, I am going to explain the basics of how the simple act of pressing a pedal can start a motorcycle.
MORE: Transmission Primer: 1933 Harley-Davidson VL Three-Speed
The quick-start mechanism is made up of several parts once it passes the starter arm and enters the transmission, so I’m going to divide the system into two main sections. The first is the starter arm assembly which, unsurprisingly, consists of the starter arm, along with a “motorcycle pedal”, a return spring, the starter motor cover, a drive sector gear. boot and a variety of bras.
Parts that make up the kicking arm assembly.
The point of this collection of parts is to transmit power from the leg to the transmission and unsurprisingly this is pretty straightforward. The kickstarter connects to one end of the kickstarter and the other end passes through the starter motor cover where the starter sector gear is bolted. Now, you don’t just want the kicker’s arm to move, so there is a two-part system that keeps the kicker’s arm in the correct position. The system consists of an external spring and a cleverly designed boot sector gear that has two built-in “hard stops”. One stop prevents the kicker’s arm from rotating clockwise beyond the 12 o’clock position, the other prevents it from rotating beyond the 6 o’clock position. Between the two stops, the kicking arm operates in a 180 degree arc that rotates counterclockwise (towards the rear tire). The spring tension holds the kicker’s arm upright and returns it to the upright position after each kick.
Since the boot sector gear only travels 180 degrees, it only has teeth in one part of the gear.
On the drive side, all remaining parts are mounted on the mainshaft and include the starter clutch, starter clutch spring, starter mainshaft gear, and a pair of fasteners needed to hold everything in place. . Basically, the starter clutch spring pushes the starter mainshaft gear against the starter clutch, causing the two gears to engage. In the photo below, you can see how the gear on the starter main shaft (larger gear on the left) has teeth inside the gear that match the teeth on the starter clutch (smaller gear on the right).
Transmission side components.
Note that the starter clutch has two square keyways cut into it. These allow the mainshaft to lock, so each time the starter clutch is turned, the mainshaft also turns. In the next photo you can see how everything looks when mounted on the main shaft. Starting from the left is a bearing on which the mainshaft is mounted, followed by the starter clutch spring, the starter mainshaft gear, the starter clutch, and finally a washer and nut to hold everything together.
Starter clutch and main starter gear mounted on the main shaft of the transmission.
PANHEAD: Tennessee, a ’33 Harley and me
As you’ve probably guessed, the starter sector gear mates with the starter mainshaft gear, so when you press the kickstarter the end result is that the mainshaft rotates. It seems easy enough, but that’s not the end of the story. Remember that whenever the motorcycle is in gear, the main shaft also rotates. So if the starter motor clutch and the starter main shaft gear are engaged, the main shaft will only be able to rotate 180 degrees between stops and not the full 360 degrees you need.
Another ingenious piece of engineering allows the starter sector gear to disengage from the starter clutch …