[TR] TR4 Starter question

[Jim Henningsen]

I know my starter needs some attention, but curious what the specific issue
is before deciding to rebuild it or put in a new gear reduction unit.  1962
TR4 CT 5212LO.  When I turn the key it cranks for a bit and then makes a hum
and stops cranking.  Turn key off and try again and same.  I can get it to
start each time but something is wrong.  Any thoughts on what is going on?
Anyone have luck with local starter shops rebuilding.  Can't imagine there
are too many parts available to them for these units.  
Thanks,
Jim Henningsen
Ocala FL 
61 TR3A
62 TR4
75 TR6
82 CJ8