can you clean carbon deposits from valves with out taking off the cylinder head

[psyfi_1]

hi guys just wondering if there is any way of cleaning the valves on me fazer with out having to crack the cylinder head off and clean its only got 20.000 on clock but i took off old carbs and theres loads of black soot in the top just under the rubber diaghram .............. is this soot build up stopping valves closing i did hear a hiss the other day from the engine
any thoughts / sugestion