The tank breather on my vfr is blocked, creating a vacuum in the tank. The tank was recently petsealed, so I'm guessing some got into the breather and has hardened. Anyone know a way to unblock it? I can't get in there with a paperclip or anything due to the position of it.
Any ideas welcome, cheers.

I've had this problem. Take off the fitting on the top of the tank where the breather attaches. This has a non-return valve in it which is probably sticking closed. Suck and blow through it 'til you can hear the valve opening and closing, no harm giving it a small squirt of WD while you're at it. Also check the full length of the breather as this can sometimes get snagged when refitting the tank.

Thanks for the reply emto, but I'm pretty certain it's the tank that's at fault, rather than the cap. If I take the fitting off, and blow through the breather hole in the tank, no air passes. When I try this on my spare tank, you can hear the air flowing, and there's no pressure build up.

maybe you could buy one of those quick release filler caps,some of those come with a hole in the cap so they can fit different bikes and that will let air into the tank for you.

Cheers for that Royster, may well end up having to.
The standard breather channel is horizontal and slightly above the bottom of the hole, I assume to make water and crap form up in a kind of 'well' rather than dropping straight into the tank. Would there be any problems with drilling another hole into the tank next to the blocked one other than it being at a slightly different angle?