Toilet Cistern Help

Where the water goes through the valve there may be a bit of dirt or the rubber seal may be gone

 

If it's a bit of muck, placing your finger over the outlet (where the water exits the ball valve) and pressing the float down so it sprays hard rather than normal flowing can very often dislodge it, might be worth trying before dismantling anything.

 

I did a quick google search and came up with this. Hope it helps.

http://www.theguardian.com/lifeandstyle/2010/jan/18/fix-a-cistern

 

These modern internals are a pain in the bum... Pardon the pun.. The damn things get tiny bits of grit which is often lime scale in them and more often need replacing..

Worst bit though is the fact they use less water in the flush. This often means flushing twice for larger theepenys ..