| pulleys
I have noticed that some belt failures are the obvious result of the fitting of pretty aftermarket pulleys.The problem is how the belts fit to the pulleys,they should not contact the belt across the tops of their teeth when they do this, I have noticed after failure, the tops of the sprocket teeth are abraided (damaged) this is symptomatic of the damage done too their adjacent running surface,-which is the kevlar belting at the bottom of the belts grooves.This belting transmits the power to turn the cams and obviously mechanical damage to this structure is to be avoided.Also as the volume of the female sprocket groves is greater than the volume of the male drive teeth on the belt, the teeth on the belt are not under compression and are much more able to be pushed over;-this cyclic plastic deformation is larger than would otherwise occur and will lead to premature failure.I believe a new belt should not contact the pulley across the tips of the pulley teeth but rather should be located radially by the belt teeth sitting in the sprocket grooves and there should be clearance across the tops of the teeth.belts also fail as tyres do as a result of total heat cycles(note 999r and the race bikes have ventilated belt covers to lessen the serverity of the heat cycles,and the belt need not perform any additional 'worthless ' work like trying to turn a damaged valve train ,obviously belt tension is critical and tricks and rules of thumb shouldnt be employed unless you know what you are doing and are prepared to handle the outcomes,anything which changes the belt friction (silicon sprays etc should be avoided.Lastly SOME BELTS ARE BAD BELTS, and if you are rude to your bike it may be rude to you ;-always wash and service your bike,whilst talking nicely to it.breakout  |