The only thing I ever attempted was to pop the sealed top off 
to check (and clean) the contacts, hoping it would cure my 
uneven acceleration (didn't work).  I've also experienced 
broken pin/vane as a result of backfiring, which required 
replacement.  BTW, I've never been offered a new one from our 
local parts purveyors - only Bosch rebuilds (about $100.)