The casting set for the smaller model had the eccentric strap and rod all as a single gunmetal casting but looking at photos of old engines this was not right. So start by cutting a slice off some 50mm cast iron bar.

Skim both sides on the lathe to bring it down to 5/16" thick and blue one side. Then clamp to a 1-2-3 block and mark it out with the height gauge.

Then over to the mill to cut away some of the waste, cut the flats where the bolts go and drill their clearance holes.

After sawing in half and cleaning up the cut surfaces the strap can be bolted together and lightly held in the 4-jaw while the hole is drilled and then bored to size.

A bit of work with the rotary table and some files soon has it to finished profile and a slot milled for the flat rod to locate into.

A piece of 1.125" bar was reduced down so the strap was a nice fit and then the offset of the eccentric marked on the end.

Changing to the 4-jaw the mark was set to run true and bored out to a nice snug fit on a piece of the crankshaft material, the boss was also machined with a rounded nose tool to give a nice fillet where the diameter meets the flat surface, I find these relatively cheap brazed carbide tools ideal for this and the angled ends make it easy to get in to tight spaces.

A couple of tapped holes at 90degrees to lock it in place.

Use a long socket head screw so that there is some thread sticking out and then make up a couple of separate heads that can be slipped on once you have tested and set up the engine to run nicely. The thread is M3 and the "heads" are from 4mm square material.

To finish off here is a group shot of the various valve parts.

I set the timing on the rough assembly, much prefer to make sure an engine runs OK before doing any finish painting as you are bound to mark it if you have to strip and re-assemble or re-work a part.

When setting up I tend to put a small piece of soft aluminium in the hole before the grub screw so it can be tightened several times on the shaft with out any damage. Once its set OK I mark the shaft where the screws touch then as I disassemble put a couple of flats where the final screw positions are.

Once it’s all painted you can put it back together without having to make adjustments, screw the grub screws up tight against the flats and then just screw the square caps on and nip them up with a small spanner which seems to hold them tight enough, no need for glue or Loctite.

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