Writing (and reading) data to any sort of magnetic media is not as simple as just writing the data bits - when reading you need to recover some form of clock so that you can synchronise to it. The usual is FM - one clock one data, MFM only put a clock when you really need it (i can't remember the rules!) RLL where you encode the data so that you cannot have more than X '1's or '0's in a sequence or manchester encoding. The old apple2 floppy controller was a masterpiece - search for info on that. The hardware is minimal and the 8051 should be able to compete with the old 6502.
You're a sucker for punishment!!!!