1990 fxr starter spinning not engageing to turn starter ring gear.sometimes spins out or just clicks?has new battery installed.starter ring gear and pinion are good.primary cover is off jack shaet is out. .can i inspect starter without fully pulling it off the bike?

very good post, few like it.
this is the starter free spinning
the solenoids job is the engage the teeth the fly wheel (ring gear)

the pinon shaft in starter is dirty, clean it (easy fix)
bad starter solenoid. get a new starter , most solenoids cost more.
your suspisons are dead on.

Check all your connections to starter and battery. If all connections are tight and the starter doesn't engage, it's time for a new starter.

Yep, not enough amps to engage the starter clutch, and when ti does engage, not enough amps to turn the engine. You need a 12 amp battery.

If the starter is spinning but it is not engaging the ring gear, you have a bad solenoid. This is to push the gear forward to turn over the engine. If the solenoid built into the starter or a separate part?

Anyway...it isn't connecting.

Semper Fi,
Z

Starter motor spins, but does not engage

1. Check the starter motor for a seized or binding pinion gear.
2. Remove the flywheel inspection plate and check for a damaged ring gear.

Sometimes they have to have little shims on them so they mesh correctly when they engage.