Here a past doc on using sysex http://web.archive.org/web/20021001211500/http://server.ats.com.au/~jonescnt/sysexman.htm

Sysex is very much model specific. You can look at the sysex chart in your keyboard manual that will tell you more about what your keyboard recognizes and what values to send.

Often keyboards also use a checksum in the sysex data totalled from the rest of the MIDI data in the sysex message. This is something a human can't really do unless the sysex data is very small .... but often it isn't. Fortunately computers are good at that sort of thing.