650 Transmission Info

The Burgman 650 has two components of a "Transmission". The CVT (Continuously Variable Transmission) of the bike is where the different "gear" ratios are made, which is the purpose of a transmission thought of by most. Another purpose of a transmission is a gear reduction, taking the higher speed of the engine and converting it into a more forceful output and providing more torque to the rear wheel. The CVT and, what Suzuki has labeled as, the "Transmission" are separate entities on the 650 despite both being part of a typical transmission. Routine maintenance on the 650 calls for changing the oil in the "transmission", but this is only for the gear reducers of the drive train, and not the CVT as it is completely dry. The gears in the transmission use splash lubrication.

The "transmission" sits in the drivetrain of the 650 between the clutch and the final drive. The pathway of the drivetrain is: Engine > CVT > Clutch > Transmission > Final Drive > Rear Wheel. Its main function is to provide a reduction in gear ratio so that the final drive is turning slower than the engine (see above). Refer to the drawing below to explain how this works.
Service Manual Image





There are three shafts in the transmission, the idler shaft in blue, the counter shaft in yellow, and the drive shaft in red. There are also four gears inside the transmission. One each are mounted on the counter and drive shaft and two that are mounted concentric on the idler shaft. In the drawing, the gear on the counter shaft is green and it meshes with a larger gear on the idler shaft, also in green. The second gear on the idler shaft is smaller (purple), and it meshes with a larger gear on the drive shaft, also in purple.

The counter shaft passes through the wall of the transmission case and has a gear on the other end of it inside the clutch housing that meshes with a gear on the clutch. When the clutch is engaged the power flows through the counter shaft into the transmission. The gear on the counter shaft drives the larger gear on the idler shaft giving the first reduction in ratio. The smaller gear on the idler shaft drives the gear on the drive shaft providing a further reduction in gear ratio. The drive shaft passes through the wall of the transmission and provides the input for power flowing to the final drive on the left swing arm.

The gears on the counter shaft and idler shaft are splined directly to the shafts to provide a solid connection. However, the gear on the driveshaft has a different mounting that provides the secondary function of the gear box. That function is to act as a shock absorber to soften the power flow. It does this through the use of a dog cam.

Service Manual Images

Driveshaft Location	Driveshaft Components	Dog Cam (top) Drive Gear (bottom)

Mounted on the driveshaft is the drive gear (black), the dog cam (purple), a spring (red), the spring stopper (blue), and a nut (yellow). The drive gear is mounted on the shaft with a bushing that lets it turn on the shaft. The dog cam and the spring stopper are splined to the shaft so that they turn with the shaft. The nut just locks the assembly to the shaft and puts tension on the spring. The dog cam has two legs on it, one on each side that fit up into pockets machined into the back of the drive gear as represented by the green cone. You will notice that the bottom of the pockets in the drive gear and the end of the legs on the dog cam are rounded and the sides are straight.

When power is applied to the drive gear it starts to turn on the drive shaft. As it turns, the legs on the dog cam start moving up the curve in the pocket pushing back against the spring but also starting the dog cam turning and rotating the drive shaft providing partial power. As the gear continues to turn, the legs on the dog cam eventually hit the sides of the pocket and at this point the whole assembly is locked together, and full power is now flowing through the drive shaft to the final drive. This slight slippage provides a cushion that absorbs the initial shock of the clutch being engaged. It also works in reverse when you close the throttle and cushions the shock when the wheel starts turning against the compression of the engine.

Review: The transmission of the 650 is actually a set of reduction gears. A dog cam device provides a small amount of slippage to the drivetrain so as to minimize jolts to the drivetrain as the clutch engages or as the throttle is rolled off to an engine braking position.

Discussion:
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