Thanks Roy, I've been trying that but unfortunately it didn't stop the carbon build up. I checked and 're adjusted my valve clearances today, same as before .008 (0.20mm) and after that the engine is running worse even though it should be the same setting as before. Also, when my engine is at operating temperature, the valve gap increases a lot, I know it's meant to but it's more than I expected. Something is definitely not right with timing and it's going to take time to get it solved.
On a different note, I bought a can of carburetta cleaner, it makes a strange sound when you spray it but it blasts all the carbon away perfectly.
