What's wrong with it? If it's worn brushes they can be replaced.
It seems there were two starters for the Paso/Sport. A series 1 and a series 2 the latter being the one with the black housing which can be also found on the Monster, SS, 851/888, 916 etc. The plate and brush set for this starter is #067050815. You can get aftermarket repair kits (which may actually be cheaper) which also include bushing, bearings and seals.
The series 1 starter had the sprocket held by a nut, on the series 2 starter it's a circlip.
Speaking about starter sprockets and back to the question. '91 and '92 750SS, 750 Paso, 750 Sport had a 15 tooth gear. On all others it's 13 teeth. So you cannot fit a starter from a >'93 SS, 906 Paso or any other unless you replace the sprocket with your old one. Not a problem if it's the version with the circlip.
If you're thinking about getting a used starter, I wounldn't. It's better fixing yours. At least then you know it's condition.

Starter is the same but check the number of teeth on the pinion, you may need to swap the one from your old starter.

Thanks gents ... will pull the starter this weekend

Check the off/run/off switch for grunge around and on the contacts. If you turn the switch to off, crank the starter then quickly switch to run wjile cranking, and it starts, you may have a fouled off/run/off switch. Mine was fouled and caused same starting issue. Cleaning resolved it. Dirty, it did not allow full voltage to the starter.

(Sorry, I thought this was paso-perhaps it still applies)

I feared my starter was toast, until I did some voltage drop tests.