I admit, my first thought was "bwahahahhaha this guy is bonkers!", But then I gave it some extra thought. Picturing anything but a Tarantino movie was difficult.
There's a lot of room for fucking up with this method: you might pull away at the last second, you might miss the target area, you might let go of the saw and throw it at something or someone by accident. It's also quite loud, which will bring people over. There's also the gore element. I mean, whoever finds you (assuming you succeed) will find human hamburger meat.
If you can pull it off, goddamn, son, you're a stronger man than I'll ever be, but I still say you should consider another, less prone to failure method.
Edit: some more extra thought: if you do succeed, patching you up would be difficult. Maybe you should go for the chainsaw, put it in such way that it drops on your neck like a guillotine, and pour yourself some hard whiskey.
No, seriously, alcohol dilutes blood. Faster bleeding. Invest in fine whiskey because you're a man with balls of fucking granite!