I have replaced my rear sprocket and have a NOS chain, now it's time to replace my front sprocket (I was running the parts that came with the bike, they're quite worn, and the front sprocket is sidecar size).  Any suggestions as to how to keep the pinion and sprocket from turning while I remove the nut?  My inclination would be to wedge a piece of wood against the teeth, but I suspect there's a proper tool or technique I'm not aware of.

Thanks,

John

Just in case anybody else has the same question I did - what finally worked for me was a $50 deep-well 1 5/8" socket from Grainger, a friend with a lathe who faced the socket to remove the chamfer, and a block of wood jammed in between the sprocket and the kicker stud.  Then the nut agreed to come off.  Simple!