With a view to getting the gearing done I made the cam gear post first. Starting with some stock that was large enough to get the rectangular head out of, I turned two diameters: the larger for the gear to run on and the smaller to go into the hole in the engine frame.
Then into the spin indexer to shape the clevis.
After reaming the pivot pin hole and milling a flat on the spigot the clevis was slotted for the latch and then rounded over.
I spent some time working out different combinations of metric gear size and numbers of teeth and in the end settled on a 50/25T combination using MOD0.7 which are available online for those that want to buy or cutters can be bought quite cheaply.
I started by roughing out a blank for the cam gear and then machined the cam profile which I made with a little less lift to suit the lever lengths of the newer head layout that has the exhaust valve further from the rocker arm pivot.
Then with the gear blank mounted on an arbor set about cutting the teeth using the rotary table with dividing plates.
The 25T crankshaft gear was cut in a similar way except I did it on the end of a bar before reaming and parting off once the teeth were done.
I like to set the gear positions using the actual gears so with a temporary crank shaft in place the small gear was slipped onto that and the larger gear on an arbor held in the mill's collet chuck and the running fit and backlash adjusted by moving the engine's frame in the X-axis. Once happy the DRO was zeroed.
After which a flat was milled and a hole drilled and reamed.
The MOD0.7 25/50 combination has a slightly larger PCD than the original design's 1" which put the hole a bit out of centre to the cast lug.
A bit of milling and filing soon had that sorted out and a hole drilled and tapped for the screw that retains the cam gear post.
PART ONE TWO THREE FOUR FIVE SIX SEVEN EIGHT
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