TW125 starter Problems

hi

my daughter bought a TW125 '99 some weeks ago and it was running fine.

Now it will not start and makes a loud noise when the electric starter button is pressed.

We have taken the starter motor apart and checked the bearings and brushes all ok

the starter motor runs very smoothly by itself.

Replaced the starter clutch with a kit consisting of three springs, three spring holders and what look like three roller bearings.

once again no luck.

jump started the bike and it runs fine.

battery is ok

the only thing i noticed was some (heat) discolouration on the large starter gear near the central hub where the starter clutch engages.

could this be the problem ????

any advice would be greatly appreciated

johnW