Nemett Lynx would be a good one to take details from though for a conversion you would probably want to put the belt at the back of the engine.

Twin cam 4-valve something like a HEMO would look good but I've not seen drawings for that.

Edited By JasonB on 13/08/2019 20:34:04

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I don't see why the small amount of milling could not be done on a lathe with the use of a vertical slide.

Barrie's suggestion of a rotary valve would save on making the cams but you are still going to meed to make a new back plate and head in either case. Just the cams that you would save on.

Yes, that is what I was thinking to drive it off the crank pin, if there was any spare length on the pin then a socket to fit over it would save having to drill the pin. I'm assuming the pin was part of the crank rather than a separate pin inserted into the web which would have made it easy to just fit a longer pin.

Looking on the web it seems that there was a commercial conversion made by a company called Stebro but that used the traditional push rod arrangement. Would be worth searching to see how that drove the gears and cam.

Why not try a worlds first:

How do you get a 4 cycle from that with the cam being on the crankshaft?

Stripped down Stebro here which seems to show a smaller pin in the crankpin but the gear block is the wrong way round to see if there is a mating disc on the pinion.

Edited By JasonB on 14/08/2019 09:42:02

I would imagine that the pinion is mounted onto a shaft with integral disc and some form of bearing is trapped between gear and the back of the disc. To reach far enough inside the hole in the disc could be extended out from the surface of the disc., may want to add a small counter balance to the disc to compensate for the extension.Sketch shows two discs so the extended hole can be seen and how they may go together. Think I would be tempted to but a bearing on both sides of the pinion either ball or bronze.

The bearing I show would fit in the backplate not the crankcase.

As you have a deep recess in the back of the crankcase the bearing(s) can sit in a spigot turned onto the front face of the backplate, this would then also move the disc further in towards the crank pin so you can then locate the drive easily.

So the backplate would look something like this on the side that fixes to the crankcase with spigot to fit the case and a recess for a bearing and through hole.

Edited By JasonB on 14/08/2019 11:21:21

Yes it was just a generic plate that would be more of a block with hollowed out areas for the gears.

Have you gone off the belt idea as the shaft that the larger gear runs on would easily take a toothed belt.

The gear scan be placed back far enough so that they don't have to fit the Merco crankcase but ideally you would not want the enclosure to be much larger than the width across the case.

If you are going for gears, cam and pushrods then have a look at the head for the Nemett "Bobcat" which is quite simple to make

I think the special had the linx in it which is the belt drive OHC, but if going for pushrods then the Bobcat/jaguar head would suit