[MENTION=389132]Bigbadjohn[/MENTION] You've got the wrong kind of blade in that sawzall.
That long blade with the big teeth is a 'pruning' blade, made for cutting quickly through green wood, like tree branches.
Metal cutting blades have much smaller teeth, like the one shown below; will make the job much cleaner.


Also, why ditch the RD? You've got a half-step triple on the front, and a wide-range 6-speed on the rear, plus a looong wheelbase. That long cage Suntour will come in handy.