Hi Grumpy
Mate I didnt take physics at school or algebra.
that method for checking timing is beyond me, even my 20 year old daughter who went right through high school to year 13(7th form) couldn't work it out. sorry mate we must be dumb.
is there any other way to check it ?

Yes the tap on the tank is leaking a little i might swap it with the other one. it wasn't leaking before i pulled it apart. the gasket or washer made out of some sort of material was falling apart i left as much as i could alone but obviously not enough.
Is there a way to make the gasket inside the tap ?
I doubt i will be able to get one anymore.
Pete