Did you buy the starter new? The ones I use come with shims that go between the gear reduction head and the starter housing. You can use the shim to move the bendix toward or away from the flywheel. With a JW wheel I have had to take the shim out. The head should bolt on with 3 bolts, remove the bolts and take the head off, remove the shim and there should also be a shim behind the bearing, take them out and put it back together. The starter I use is not a powermaster, but a CSI, but they are built the same way I think.
Randy