I am going to replace the stock rear sprocket (42 tooth) with the same style but a 43 tooth. Do I need a larger chain or just a matter of an adjustment in tension?

thanks

 

One tooth, probably not, unless you are at the limit of chain adjustment. I usually
change the drive sprocket and not the driven sprocket for a more noticable
change. Never had to change the chain.

Either way, install the sprocket and see if it fits. If not, you can use two master
links or a half-link to make the chain slightly longer.

 

FYI: 3 teeth on the rear sprocket = 1 tooth on the front sprocket.