Sprocket Size

[Mark M]

I went down an bought a new 18" bar and chain for my old Jonsereds 630 and also got an 8 tooth sprocket. The old sprocket for the 16" bar and chain was 7 tooth. I seem to remember seeing it written somewhere that the longer chain should be used with a bigger sprocket but that doesn't make sense to me. The new combo seems to work well but I would have thought if anything you would use a smaller sprocket with a longer chain. Any comments?

Mark

[Kevin]

Mark,
A larger drive sprocket uses a longer chain.
With large drive sprockets there's more of a chance that you could throw a chain.
Make sure your oil holes still line up.

[jokers]

Mark, your way of thinking is right. A larger sprocket gives a numerically lower gear ratio meaning higher chain speed and less torque. You are getting away with the 8 tooth rim because an 18" bar is on the smaller side for your 630.

Kevin has good points about chain throws and oiler hole alignment but I haven`t seen these things to be a problem when running an 8 tooth vs a 7 tooth rim. Chain length isn`t normally an issue either except when running an 8 tooth on an 026 with .325 chain. That combo is very tight until the chain stretches. Any other saw I`ve run an 8 on hasn`t been a problem.

Russ