It may be your starter clutch as well. When I hit the starter button it had a grinding noise and then eventually just a zing and it wouldn't start. It turned out to be the starter clutch. The bolts had sheared off and the starter motor couldn't engage the engine. I really hope its not the starter clutch because its a pain to do and expensive.
What year is your bike? Got any video of it?
It is 1988 i have checked the starter motor and it was very dirty inside will leave it to an mecanic to get it checked