I have an '88 FLT with constant starter problems.
I'm thinking of switching to an '89 or newer inner primary to be able to use the newer style starters. Anyone ever tried this? Any thoughts?

 

If you decide to do it, I suggest you find an inner primary cover before you buy any starter parts.

Once you have that inner primary cover, you can look for starter parts for the same model year.

What is the problem with the existing starter?

 

I have replaced the starter with an All ***** 1.4 kw, replaced batt., solenoid and cables. Checked for proper grounding, and still it barely turns over unless I leave out the solenoid return spring.
I finally sent it to the best wrench in the area, and after he replaced bearings, seals and plunger, and tried every trick he knew, he finally gave up.

 

If you haven`t done it already, replace the starter relay.

Trace the wires from terminals 87 and 30 on the relay, make sure they are in good condition, and connections are clean and secure (the juice passing through these wires is what controls the movement of the solenoid).