you could try spraying something like eazi start directly into airbox and immediatley try to start the bike..

if it catches/starts then you know the batteries ok.

my friend,who bought his bike after i bought mine has just text me to let me know that his fully chrged battery has died,held a charge/tried to turn over the bike for all of 5 seconds before doing sweet fa..

Yuasa �55 at Halfords...