I have a MC21 SP with TA22B carbs. Looking at the floats with the float needle at the top, there is a brass tube forward and to the right of main jet. This tube seems to be deliberately blocked with a compound judging by the hardness. On my R5k carbs, TA21A, this tube is clear and extends internally up into the bellmouth in at least 2 places. One immediately behind the slide and one at the top facing backwards next to a larger hole. Is this a modification ie one of the differences between the two models. The more obvious one is the, still there but not machined, breather opposite the air screw.
Any help would be appreciated.
Thanks
Alan
PS If this is in the wrong section please advise as this is my first technical query.