New starter sprocket

The starter engage-sprocket was heavily damaged on the engine that I bought.  It was severely knocked out of line and had badly chipped teeth (someone suggested it looked like an idiot might have tried to free a seized cylinder by whacking it with a hammer and cold-chisel (another reason I was keen to get the crank-shaft balanced)
And so I was committed to repairing or remaking a new sprocket.

For some reason the sprocket on the flywheel was in two parts (were they designed as pressed pieces 'laminated' together?).  I decided to make my new one in one piece - 7.5mm thick steel plate.






A couple of hours sawing and filing and I was ready to go.  However I was a little concerned about the new sprocket wearing faster than it should, so I decided to case harden it.

There are plenty of tutorials on case hardening on the web ( here is a nice simple explanation of how it works) However I chose this one because I had some charcoal.  It was all a bit school-boy experimentation with oxy-acetylene and steam and stuff, but I enjoyed the process.  Whatever the outcome of the metallurgy exercise, the best way to ensure it doesnt get too much wear is clearly to build the bike up to be an easy starter.... but thats a whole different problem

The original sprockets were riveted in place.  I chose to use M4 stainless steel button head socket screws, with a good dob of lock-tight to ensure they don't come out accidently