I've got the father in laws 1986 Jonsered 670 here. When I'm done it's going to be immaculate, and it HAS to run perfect. I can take care of that. He says he's taken a carb off I think a 70e and fit it up to this saw. I'm gonna have to take a close look and see what he's done. I know some saws have simple little tricks you can do to them to squeak out some easy power gains - anybody know of anything for this model? I'd like to keep away from the traditional muffler mod as far as noise is concerned. I may open up the inside a little bit but don't want it crazy loud. The saw is going to be given to my brother in law as he will be burning wood starting this coming winter. I'll keep ya posted on the refurbing of the saw as I go. Lots of pics with this one hopefully.