Another version of how not to build a model engine

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sorveltaja:
New crankcase cover in place, after some cleaning:

While inspecting other parts, I noticed, that both piston top and brass button had clear mark on them, caused by knocking on each other. Not good.
That should not have been possible :scratch:. Anyways, I lowered the brass button about 1mm or so, to make sure, that it and piston doesn't get a chance to knock anymore:

sorveltaja:
So far, but not so good; when assembling the engine, piston didn't fit to the cylinder anymore, as it did before.

Cylinder liner is bent on its lower part, being more oval shaped, than round. I guess, that something went wrong, when I did the recent sealing/tightening with it and the cylinder head. Cylinder liner has only 0.5mm 0.2mm(~0.0078")wall thickness, so no wonder, that it finally gave up:

Just another unexpected weak spot in my design :wack:.

Not sure, how long it takes, but I'll have to make a new cylinder liner and piston, as current ones are now useless.

During this project, I've somehow began to get used to make new parts, as needed.

Cylinder/piston fitting is one of the most challenging thing to do on any engine, but then again, I consider it as a good chance to practice my skills.

I'll post the process pics as soon as I get a chance.

sorveltaja:
At this point, cylinder lapping is at the stage, where the surface begins to be satin smooth, and almost even:

Bore diameter will be 0.5mm smaller, than on previous cylinder, thus allowing the old piston to be re-machined, and fitted.

sorveltaja:
Todays effort:

New brackets are made of 1.5mm(~0.059") mild steel, to add more rigidity, while previous ones were made of 1mm(~0.039") brass.

Next thing to do is to drill screw holes to both bracket, and file the excess material off.

sorveltaja:
As can be seen, once a perfectly working cylinder has now became two sacrificial drilling templates:

New brackets were super-glued in place, before drilling. Screws on the above pic are there securing, just in case, if that gluing gives up.

So it's time to start the filing process.

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