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
Another question when mounting the startermotor togethrr again it is a metall round thing that should fit in in the bottom of the starter but the strong magnet make it impossible to get it to stay in the right position any trick to get it right ?