hi,,,,clean yr chain and sprocket with the disel oil,,thast how
i celan it,,,,clean everypart of it and the chain,the disel oil
will make the dirts and grease come off,,,then after cleaning apply
some engine oil on it,,,no need to put too much chain lube,,,just
put some engine oil,,,but have to check wether the chain is dry or
not once every 3 or 4 days,,,this works for my chain and
sprocket,,,,no problem so far,,,more then a year already,,,
and if u kept on hearing sounds,,,check wether is it
the brake pads got problems or maybe is the wheel sub bearings have
broken or not,,,this happen to my aprilia last time,,,then can feel
the bike is unbalance and when moving off or stopping can hear
noise from the back,,,commmonly its the brake pads which is not gd
and it makes sound,,,but have to depends,,,sometimes when the pads
have some sands in it,,,the sands will make noise when u
brake,,,just take the pads out and wash then fix it on
back,,,should bee no more noise unless its something else,,just
like wat i say above,,,
either bearings had broken,pad got sand,sprocket teeth if
become sharp on the ends already then pls change,,,cos no matter
the chain u change and never change the sprocket,,,,still the chain
will become spoilt in no time,,,this come with my experience,,,my
aprilia had change 3 times of chain,sprockets in 2 years,,,and 1
time sub bearings....lucky i sold it already,,,,, 
ps.....above mentions things are to be varifed by different kind of
bikes,,,, ;P