Let's brainstorm.

[Triple]

Originally Posted by askmrjesus

If you can't fit a puller in there, grind the arms down until they fit.

Others have tried this, and the puller generally bends/breaks before the cog moves. This is a fairly common problem with these cars; it's the result of a botched crank-nose repair. Liquid metal used to fill a worn key-way bonds the cog to the crank if it's installed before everything cures.

Originally Posted by 101lifts2

I cannot really see from the picture, but are there 4 threaded holes in that sprocket?

I believe older Miatas had threaded holes in their crank gears for this very purpose. Mine does not. I only found one hole and it wasn't threaded; I think someone else may have drilled it in an attempt similar to mine.

Originally Posted by Turbo Ghost

When you tried the heat/duster trick, you needed to cool the shaft not the gear. The gear needs to be hotter than the shaft so it's bigger. You might also try (if there is room) heating it then striking it with a hammer back towards the motor to shock it loose. You could also take a dremel and cut a slice down one side then split it with a chisel and hammer. Good luck!

I tried most of what you posted.

I ordered a 4-inch angle grinder with some cutting wheels. Here's hoping I don't damage the crank in the process of cutting the gear...