i just restored my WM-55. it plays good with C90 cassettes. yesterday i recorded a C120 tape, and .... weeeell ... think its a bit, just a lil bit jerky ... is that normal, or do i have to disassemble again ? ...

C120 tape is extremely thin tape. Nearly most all cassette drive manufacturers do not recommend use of them.

If you must use C120 tape be sure that your capstan is free from all tape oxide deposits and that the pinch roller is free of all tape oxides, grippy, soft and dull coloured. If the pinch roller is hard shiny or has contamination then you will experience playback problems and possibly tape damage more so with C120 but probably likely with any other tape length too.

thx for the info ...

well, it`s just freshly cleaned. i dont have any problems with them in my sony DDs, so i thougt, that 80s walkmen should be strong enough to pull the tape ...