| Having chatted to local mechanic he too suspects the lack of the tank to breathe. Cant see any way to remove the ball bearings but will have a good look.
Cut open and inspected the fuel filter. Learnt its ok to blow through the fuel filter but sucking is a silly thing to do.
Little bit of rubbish on the tank side of the filter (need new filter now I have cut it open.)
Tried blowing past the ball bearing from both sides but to no avail. Definatelt lack of air. Get a good old hiss when I open the cap. I suppose drilling out the ball bearing is not acceptable on a race bike.
Cheers
Mark | 
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