A sprocket wrench to hold the sprocket while loosening the drive side crankshaft bolt

Here is my sprocket wrench, made from a length of square tubing, a chain and an old wrist pin.
To get the right fit you can play with the length of the tubing, the length of the chain and the diameter of the "pin" (use a piece of wooden dowel?). This one cost me nothing because I had everything lying around... I didn't even have to cut the tubing, what I had was just about the right length. It is a bit loose in the pictures, but it worked like that. I used an old wrist pin with some tape wrapped around it to block the chain at the other end of the tube... I should try something a bit larger to tighten it up.

The engine in the picture is a JICA engine with a clutch, the sprocket wrench would be of no use on it... but it was the only engine in the house with a sprocket on it...