Casting flash

I am very tempted to cut some of it away as the passages with the flashing are quite a bit smaller than the ones without. The engine did run pretty hot. I always had to keep the fan on below 30mph. It may not be these partly restricted water passages. but I suppose it won't harm the heat issue by opening them out a bit.

If you REALLY want to do this, I would suggest you get a piece of bristol board and lay out a template for one cylinder. Mark out the diameter of the combustion chamber and while you're at it also mark out the diameter of the cylinder bore. Layout the inner diameter and outer straight edge of the water passages. I wouldn't get too concerned about the finished ends of the passages because you will blend in the ends of the existing passages when you go to grind. Finish the template by cutting out the combustion chamber and the water passages as laid out
You'll need some layout dye. Put the layout dye on the cylinder head around the existing passages and let it dry. Place the template on the head locating it in reference to the combustion chamber and scribe out the material to be removed as per your template.
Double cut carbide burrs are a little more easy to do this work with than single cut from my experience but single cut burrs will do the work if that's all you have.
After you reworked the head you could then cut out the diameter of the cylinder bore that you previously marked on the template and then check and /or rework the passages in the block.
anyway, that's the way I would tackle it IF I chose to do this mod. It's not a bad idea but I'm not sure if it's worth the trouble. Could be just what the doctor ordered, I'm just not sure.
KB

Thanks Kawboy. for your thoughts on this, I'd never heard of Bristol paper before. I do have to get a better cutting tool too.
I couldn't resist and had a first stab at one of them yesterday with my dremel tool and a totally unsuitable tiny cutting tool. Keeping the dowels in place and the old gasket down for safety more than anything. It was strangely satisfying to remove the flashing. I won't go too far neatening it up and looking for perfection, as I don't want to push my luck, but it does look and feel better to me. It'll be interesting to see if it makes the difference.

Bristol; board is a type of cardboard like construction paper we used as kids for school presentations. Came in multiple colors. heavy enough to stay reasonably firm and cut easily with scissors or an X-acto knife Came in 24" x 36" sheets.

Nice job on the cleanup. If it took you longer than 10 minutes, yes wrong tool. I have a 1/4" die grinder air powered that would knock that off in 5 minutes easily. Never did a cylinder head or 2 stroke cylinder without reworking the ports.

Thanks! It took me about half an hour as my dremel type cutting tool is tiny. Then a cleaned the rough edge with a small file. I have a die grinder but no cutter small enough to fit the water passages.
I think I'll have to go and find one or this job will loose it's novelty quite quickly.