Petrol cap blockage

[Revvers]

Hello. Took scoot out, sounded very 'lumpy' and lacking in power, then ground to a halt. I removed the petrol cap and all is fine. This is the fourth time this has happened to me and I have tried 3 different caps including 2 Casa ones. It appears that the tiny breather hole in the handle is getting blocked (?). Any ideas as to why this should be happening? The painter I used had left some bead in the tank which I thought I'd removed, it couldn't be tiny particles of this going up into it surely??
Also, my speedo light bulb flickers as I go along. Is this a purely bad connection or indicative of another issue? Cheers

[missing lynx]

hi the speedo is more than lightly a bad earth try running a an independent earth and not rely on the cable to do the job. with the cap what seat are you using and are you using the std filter box

[Revvers]

Yes, all standard. The seat is a Geuilianni (??!)All was ok until I had the scoot painted. Same seat and airbox
When you say a separate earth for the speedo, I have a Cambridge Lambretta speedo with a specific terminal on the speedo bulb, earthing straight to the headset

[Shaun]

I have failed loads of fuel cap seals recently, I take the caps off to check on the MOT and the rubber seal seems to triple in size and I can't refit the cap.
Is your rubber seal expanding when in use and being splashed with fuel, but shrinking back later??
Just to try, can you drill a larger hole in a faulty cap, not in the handle and see if that helps.

Shaun.

[Revvers]

That makes sense Shaun. Thanks. Will get drilling