The two flywheels had a fair amount of thin flash. So the first thing I did was to take a small cross-pein hammer and carefully chip the flash off. This shows the one on the right after chipping and the left as delivered.

I then fettled the flywheel. I like to do this before any machining as it saves marking the finish turned rim if you intend to leave that bright. It was mostly done with files and then a quick tickle with the Dremel equipped with a grinding bit, again one on the right has been fettled. There is a little more to do between the spokes where they meet the hub.

Where possible I like to hold flywheels by the inside face of the rim and get that to run true as it is not a surface that is going to be machined, this is another reason to clean them up first. With the 3-jaw's jaws reversed it fitted easily and was just tapped on the side until it ran with minimal wobble.

My machining sequence was:

1. •Rim OD, Rim Side both these done with CCGT inserts using the holders that make use of the two ‘spare’ corners.
   

2. •I then changed to a boring bar with 0.8mm corner radius CCGT insert and flattened off the side of the inner rim, this ended up 1.75mm below the side face of the rim.
   

3. •The hub was then faced, spot drilled, drilled 6mm with a stub length drill, opened out to 9mm and then a boring bar used to take it out to final 10mm dia using the crankshaft material as a plug gauge to get the fit right which is tighter than a nominal 10mm reamer gives.
   

4. •Lastly change to a brazed tip tool with 1.5mm nose radius, set the top slide to a few degrees and clean up the OD of the hub. Knock off all corners in the lathe with a a file.
   

To do the other side I changed to the 4-jaw and got the flywheel OD running true before machining Rim side, recessed side, hub face, hub OD.

With two done it was time for a trial fit

I needed a way to mount the belt pulley so clamped the non governor side flywheel to the mill table and located its centre and ensured two opposite spokes were along the Y-axis. The DRO made quick work of spotting, drilling and tapping the three holes at 120deg spacing and then I went round again with a 3-flute milling cutter to form a counterbore.

Some short lengths of 10mm steel were drilled M3 clearance and then bonded into the counterbores with JBWeld and left to set for 48hrs.

Once set the flywheel went back into the 4-jaw on the lathe to have the three bosses machined to length and also a small step turned that would locate the ID of the pulley.

And with the Pulley in place.

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