geez HP...you don't make 'em ezy do ya..
so
ok here we go
Carbon is something that occurs in petrochemicals
(aka hydrocarbons) and
as a byproduct of the heating or burning of
petrochemicals...aka motor oil or fuel (petrol or diesel)
carbon in ya carby generally comes from the fumes of the fuel
collecting as a type of varnish or coating on the carby innards
and is cleaned out using a solvent type carby/inlet spray cleaner
get one at repco or autobarn or Bursons etc
carbon is also a by product of heating motor oil
and over time will collect on surfaces inside an engine
and the only way to reduce this is to change oil..often
and
to remove it?..is to rebuild your engine
although some swear by cleaning oils...I don't coz they dont
lubricate when cleaning
carbon in/around a heat exchange (ya motor) which uses
hydrocarbons is quite normal
hth
cheers