Gearbox Question Grinding Me

[Fazerider]

On the subject of gears, used to read about straight-cut gears, and how, particularly on Kawasakis of the time, they used to cause that characteristic whine Kwaks were known for. So what is a straight-cut gear, what other types are there, advantages/disadvantages/reasons for using one type or another?

Straight cut gears are what we have. They're noisier because the whole width of the tooth touches its mating gear's tooth at the same time.
Helical cut ones mesh gradually. They're less efficient because some of the torque gets turned into an axial force.
Car gearboxes are generally helical except for first gear where that is the one used to provide reverse (introducing another gear wheel means it would be required to have the opposite cut) so that's why cars are extra whiney when in reverse. Dunno why older Kawasaki's should be particularly bad though.