I put up a long post about it a few years ago-You could find it in the archives useing ram starter and my sign on. In my opinion that starter was a major contributing factor to the RAMs problems. That little flat O ring just did not make good contact on the flat compressor nut. Tons of slipping, low RPMs and FLAMES from that.
It is not an easy fix. and I am not sure the spring is the issue. Please check for vibration and that the ECU is fully braking the starter.
You cant get the Bendix off without destroying the starter moter. and that Fulhaber motor is a bb coreless design that costs $119 USD. The Bendix has been press fit with a non removable locktite on the shaft.
You could try and pull the bendix off by drilling two small holes at the base of the cone to allow access to the end of the Bendix, then heat up the bendix with a minitorch or iron to soften the glue and then try to pry it off the shaft thru the holes with small screwdrivers. Might work.
The other option is to have Carlos put on an X style starter. About $500 for parts and machining and balance that will need to be done. The engine will start like a dream then though. Scott