1.5.2 Motorcycle Chain
Transmission
Application Examples
Motorcycles are high-speed applications that operate in tough conditions—rain, dirt, sand, and high shock loads. These specially developed chains are used as the part of the drive train to transmit the motor power to the back wheel (Figure 1.19).
Motorcycle Chains are superior to gears, which are in the crank cases, by the ease in adjusting the shaft center distance and the number of teeth of the sprocket. Therefore, you can freely design the motorcycle's reduction ratio taking into account the specifications and the working conditions. In the case of a racing motorcycle, for example, the engine power may be 180 hp, and the chain speed is 1,500 m/min.
Figure 1.19 Motorcycle Chain in Action
Construction and Features
Motorcycle Chains have the same basic construction and sizes (numbers 40, 50, and 60, Table 1.9) as Standard Roller Chains. But they have a special width of inner links. Because of the very demanding working conditions, some Motorcycle Chains have the following special features:
- Strength
Quad-staked riveting on the pin head helps to retain the link plate on the pin. Connecting links are press fit. (Riveted connecting links are also available.) Link plates are thicker (heavy) and the rollers are seamless. - Wear life
Special coated pins, sintered bushings that are oil impregnated, and seamless bushings with O-rings are used to extend the wear life of the chain. - Resistance to dirt, sand, or mud
To prevent debris from getting into tight joints, the bushings are extended beyond the inner link plates, and often O-rings are used to seal the chains. This extension and O-rings prevent abrasive material from getting into the chain. - Appearance
These chains may have special coloring, plating, (gold or silver), or glossy finish on the plates.
| 40 Class | 50 Class | 60 Class | |||
|---|---|---|---|---|---|
| Chain Number | Inside Width (mm) | Chain Number | Inside Width (mm) | Chain Number | Inside Width (mm) |
| 420 | 6.35 | 520 | 6.35 | 630 | 9.53 |
| 425 | 7.95* | 525 | 7.95 | ||
| 428** | 7.95* | 530 | 9.53* | ||
* Same inside width as ANSI Standard Roller Chain
** Roller diameter differs from ANSI Standard Roller Chain
Sprockets
Special sprockets are used for these chains. Numbers 425 and 530 sprockets have the same tooth shapes as standard types.
Selection and Handling
- Usually the specifications differ for each motorcycle or application, even with the same-sized chains. Do not select the chain just by size of the sprocket; take into account the application. For example, an off-road motorcycle travels through dirt and sand, which will get on the chain. You should avoid the use of oil-impregnated sintered bushings for this application.
- Failure of Motorcycle Chains may result in injury or death. Care must be exercised when connecting or aligning the chains.
- Both O-ring chains and oil-impregnated sintered bushing chains wear rapidly if the O-rings fall off or if the oil in the sintered bushings is depleted. If either of these situations occur, the chain must be replaced—even if it has not elongated to the limit.
- The life of O-ring chain is usually determined by the durability of the O-ring. To improve the durability, there should be an oil film on the O-ring at all times. Even though it is a sealed chain, lubrication is required to extend the working life of the O-ring. Cleaning sprays may cause deterioration of the O-rings. Do not allow chains to air dry after washing, or to rust.
Technical Trend
Motorcycles are getting faster and more powerful. Therefore, Motorcycle Chains must have greater durability. At the same time, motorcycles are getting lighter and smaller. Manufacturers are working on new materials, sizes, and heat treatments to improve the performance of the chain.
