new clutch now starter dont turn but engages
 

I just helped a buddy put a clutch in a 98 tiburon just like I haved done in countless other cars and when we got it back together the starter would thump but not rotate or turn the motor then I rotaed the motor at the crank pulley and tried again and it started so we thought that maybe the starter gear just wasnt meshing with the flywheel so we shut if off and tried to start it again and the same thing. Battery good, starter checked good, pulled tranny down and everything good, resistance good in power and ground wires good power at starter.Any help would be great. Thanks