Husqvarna older drive sprocket?

[Oldtoolsnewproblems]

So I got curious about trying an 8 tooth on my 266se with the 15 inch bar, and realized my backup saw has a super worn drive sprocket so I bought a few 7s.
Attached is a pic of new vs old and I have two questions. 1) how much life does the old one have left?
2) is it the wrong style? The new one doesn't have the relieved back, but it seems to fit. Is it just a cheaper style?

 

[Oldtoolsnewproblems]

Oops, looks like they didn't attach

 

[Oldtoolsnewproblems]

I continue to be dumb, as none of those actually show the difference between the old one and the new one. Old one is the one with the relief cutouts in one side

 

[Ronie]

You can use the ones without the cut outs. I've read that the cut outs help remove chips but I don't know how true that is..

 

[Huskvarna hotellgäst]

I continue to be dumb, as none of those actually show the difference between the old one and the new one. Old one is the one with the relief cutouts in one side

The one with the relief cutouts is over 35 years old. Oregon changed to having cutouts in the centre of the drive link slot on the outer edge in about 1985. This made them stronger without increasing mass. Use one of the new ones.

 

[Oldtoolsnewproblems]

35 years old? So what I'm hearing is it's a classic, great vintage, highly collectible? Put it on eBay for$300

In all seriousness, is it still in good shape tho? I replaced it with a new one to see if it felt any different, I have a basically new chain on it, and it felt a little chunky when I over tensioned it, will see if it smooth out after a tank or two goes thru the saw.