Thank's Michael, I did my usual copy and paste from my post over on MEM where from comments last night I knew they are showing.

When drawing up the engine I played with a few options for the cylinder, I did think of doing an aluminium finned outer with cast iron liner but it would not have been easy attaching this to the frame and the same problem would have existed if I went with an all cast iron option. In the end I settled on a steel finned outer which could be silver soldered into the frame that would accept a cast iron liner.

First job was to saw of a length of EN1A steel with sufficient length to allow it to be held in the 3-jaw while a spigot was turned to locate it in the upper part of the frame, here you can see me using the frame to gauge the fit.

Then with some added tailstock support the fins were roughed out using a 2mm GTN type parting insert.

Changing to a 2mm dia MRMN tool the sides of the fins were tapered and the valley rounded to give the "cast" look

The chucking piece was then sawn off and the cylinder outer bored and a spigot cut to locate into the lower part of the frame.

The next job was to make the various webs that stiffen the frame, these were located into shallow slots milled into the inner faces of the frame and shaft bosses, here you can see a couple in place, the crests of the fins have also been rounded over.

After completing the webs and adding more bosses for the valve guide and fan spindle it was time for a bit of silver soldering.

I could now treat my fabrication as a casting. After sawing out the spacers between the bosses the inner faces were milled back to length then the frame held flywheel end upwards and the shaft holes drilled and reamed. If you look closely particularly at the cam shaft boss that I tried to hide with the milling cutter you can see that things moved slightly during soldering but that protruding boss is due to be flushed off so won't show.

The bottom was given a quick skim and the mounting holes added

I opted for off the shelf gears as they are cheap particularly as they were wide enough to cut down the middle so I have some for the next project, some make shift shafts were slipped into the holes and gear mesh checked out OK.

Continuing to get some use out of the KX3 some of the smaller parts were then made with its aid.

For the conrod a piece of round 2014 had flats milled on either and was then drilled and reamed for big and little ends. it was fixed to a holding block with a couple of top hat bushes and given a pleasing shape.

Followed by turning a couple of bronze bushes that were a lightly pressed in with a drop of 648 for good measure.

Unlike the original I wanted to be able to adjust the ignition timing while the engine was running and the curves on the timing bracket and a small brass knob for the adjuster were again ideal CNC jobs.

The Rocker arm was next up on the list being held at either end on an overlong blank that had the waste material cut off after machining.

The piston was a simple turning job but I did use the CNC to mill out the dog bone shaped internal recess, here it is along with the other small parts.

Another feature I wanted to add was a small cooling fan which was cut from 0.5mm steel steel, a few tabs were included in the code so that it would remain in place while the 2mm cutter worked it's way around the shape, these were simply cut through and the remains filed off to finish.

Just a small post tonight. I was not that keen on the fuel tank or carb shown on the earlier engines so I decided to go for something similar to what I made for the Midget not least because I still had five of those miniature jam jars to find a use for!

Apart from having it screw into the cylinder head rather than use a flange mounting the only other real deviation was to have a lever to rotate the throttle barrel rather than using the actual jam jar. The CNC made quick work of this with a 3mm 3-flute cutter blending all the internal and external radii perfectly, I set the CAM to leave a couple of tabs so the part did not fly off part way through cutting and these were easily cay and removed with a needle file.

I used a piece of 8mm copper brake line for the exhaust which was filled with lead to stop it collapsing while being bent over a former. The lead melted out without sticking to the uncleaned copper so it was easy to silver solder on a short length of brass drilled 6mm and threaded M8 x 1.0mm so it could be screwed into the head and like the carb locked with a round nut with two spanner flats as I felt that looked a bit nicer than the usual hex nuts.

That just about completes the construction. I have test run the engine but did not bother to video it, these tests did show that it gets quite hot so my hopes to paint it in Kawasaki green have had to be put on hold as I felt some VHT paint may stand a better chance of surviving and their "kermit" green is not as bright . Now that the paint has had time to harden I'm waiting for a bright day to take some photos before the paintwork gets mucked up with oil etc doing the video run but hope to have pics and a video for you soon.

Yes I'll be leaving it exposed, adds to the interest if you can see what's going on even if it's a bit messy.

Thanks for all the appreciative comments

But onward to the important bit before anyone thinks Unlike a few engines this one seemed to run better after stripping and painting and starts first time after a pull of the cord which I can get 5-6 winds around the starter pully. It's still running quite hot particularly when I lean it out which also ups the revs and makes the throttle a bit more responsive. Richening the mixture a bit slows it down to a more pleasing (to me) speed but then the throttle has little effect.

I did not play with the timing on the video as it is hard to do up the adjuster one handed and did not want to risk things coming loose as during initial testing that did happen and the brass ignition contact went through the open gears and was spat out the other side in several pieces

The exposed gears and crank make it a bit noisy but it does make for a more interesting engine when running rather than having everything hidden away inside a crankcase and the dirty oil seems to wipe off Ok

For the liquid fueled IC engines I tend to use Colmans fuel which is available from most camping and outdoors type retailers as it is used as a camp stove fuel.

The Americans sometimes refer to it as "White gas" as it is almost colourless unlike pump gas (petrol) but the main reason I use it is it smells far less so you don't end up with a workshop smelling of petrol fuels and if you bring the engine into the house for display/storage there is no lingering smell.

As this is an open crank 4-stroke I am running a very small amount of Husqvarna 2-stroke oil and after about a min into the running you can see I've filled up with a slightly stronger mix as there is more of a green tinge to the fuel. Some people add WD40 or the Americans like their marvel Mystery Oil.

As far as the ignition goes I tend to use the CDI ignitions from S/S in the States this being their single spark unit, you can just see the outer cover of it laying over the battery holder though they are winding the business down and retiring. The unit can be tripped by a hall sensor but also has the option for a pair of simple contacts just by using 2 of the three wires that would have gone to the hall sensor and I much prefer to do it that way. You don't need anything fancy for contacts like you would with a traditional car coil, just two metal contacts, on this engine I have a fixed brass stud in the side of the larger cam gear and an insulated flat brass strip contact on an adjustable are so that when the two meet the circuit is completed and you get your spark.

Power comes from four AA batteries and I'm using a standard length 1/4 x 32 Rimfire sparkplug with one of S/S's silicon boots as the plug is a bit too close to the exhaust rocker you a more traditional looking brass clip causing the spark to take the easy route and not happen inside the engine. There is a ground wire that completes the circuit back to the CDI which I've just got hooked up to one of the cylinder head screws for now.

Nearest equivalent from a UK source now that S/S are winding up would be the MCL-1 unit done my Minimag