Carb Rebuild Question

Do anyone know if the carb rebuild kits come wiht an o-ring for the little window?

Also, if i get a good working carb, should i just rebuild my carb, or the new "used" one that I get?

yes, the kits should have the o-ring.
if you just need o-ring. you may be able to get just o-ring from autozone.

It's all screwed up enough that I am just going to do a rebuild.

there is more than one leak, i'm sure.