help with gears

[ruffers]

When in certain gears or selecting certain ones there is an annoying rattling/catching noise coming from the chain is this a fault or is it me not using gears correctly, my bike was second hand when purchased and I am yet to have it serviced, would this be wise and what should I expect from a service and how much to pay? Thanks in advance for replies.

 

[simon.r]

It probably just needs the cable tension adjusting - sounds as if the chain isn't settling on the sprocket properly.

See the section titled 'Index Setting' towards the bottom of this page: http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

A service probably wouldn't hurt, but there are plenty of guides on the web that will help you give the bike a check over and see if anything needs doing before you start paying for it.