Stuck sprocket - need advice

[sanddrag]

Okay, I've had lots of really stuck sprockets, hubs, gears, whatever in my time but nothing like this one. I'm trying to take apart this old lawnmower I have (to make a gokart) and one of the sprockets is so stuck on its shaft that it might as well be welded on. This would be a good thing in the future because it will be a drive sprocket/axle but right now it is bad because further down the axle there is a sprocket welded on, and between the two sprockets is a wheel that I need gone. So, I must remove the stuck sprocket to get the wheel off (and install a spacer in its place).

The stuck sprocket has two set screws at 90 degrees from each other which I removed completely. I've tried beating the shaft out of the sprocket. I've tried beating the sprocket back down the shaft (so then I could grind the shaft a little smaller). I've tried twisting it by holding it and the shaft with two Robogrip pliers (and I'm a strong guy too). I've tried WD40. And none of these methods even caused it to budge.

The only thing I haven't tried is heating. Should I give it a shot? I'm afraid the shaft might heat up too and that I could run into the problem of the shaft steel have a greater coeficient of linear expansion than the sprocket steel and that would make the problem even worse.

I don't have access to an arbor (or any other kind) of press right now. Only my muscles, and hammer, robogrips, dremel, sawzall, etc.

I don't really care about saving the sprocket (because I have an identical one) but I do need to save the shaft. So would it be possible to cut the sprocket off with something like a sawzall?