Im currently dismantling ,with a view to cleaning , the four carbs on the above motor. I have the bowls off and there was no obvious debris in the bowl. I have removed the end cap to remove the low and high speed emulsion tubes. But I cannot get the emulsion tubes to come out. The low speed tube has an oring at the end of it and I can withdraw it slightly but no more. I was under the impression it would simply fall out ,been kept in by the bottom cover screw.What is keeping the tubes in? Any suggestions would be most appreciated? Nik