Today I received the package of assorted tape drive belts in the mail. None of the belts in the package were a direct fit for either set of pulleys so I trimmed the next largest sizes and spliced them with super glue.
The trimmed belts seemed to fit well, but there was still a very noticeable fast flutter present in playback. I searched for more causes of flutter and found that a poorly oiled capstan bearing may be to blame. I oiled the pinch roller and capstan bearing on the Sony with synthetic 0W-20 oil. I found that a lightweight motor oil was recommended on a couple forum posts.
I didn't hear an improvement after oiling the bearings so I started to grease the plastic parts. I took apart enough of the mechanism to remove all the plastic pieces then cleaned them with alcohol. I got too heavy handed with one of the plastic gears and broke it during cleaning.
I made an attempt to glue the gear together with superglue, but I did so carelessly and ended up misaligning the pieces. I put the deck back together with the sloppy gear with poor results. The tape repeatedly jammed and got stuck in the roller.
I have ruined the Sony deck -- not beyond repair, but beyond care. The Sony TC-FX160 isn't a great deck to begin with. I simply don't wish to put anymore time or money into trying to get a $3 thrift shop find working.
I would switch to the Panasonic deck, but the transport on it needs work. I'm pretty tired of blindly hacking at cassette decks or I would give a shot at lubricating it. I'm still in search of a decent recorder for this project and long term use. Hopefully I'll have some luck junk shopping soon.