How do I remove the front sprocket on a Dinli Helix 90? I have the chain off but the sprocket just spins. Is this a reverse thread bolt? How do I keep the sprocket from spinning?

 

What I've done is take a large screwdriver and rest the tip against something behind the sprocket and then place the shaft in between the teeth of the sprocket. Then loosen the fastener. There's probly a better way, but this works for me.

 

I got it using a pipe wrench