DragBikeMike wrote on Yesterday at 13:23:46:


And a small increase can, have major consequences.
longer flame path.
larger “end-gas” zone (the last mixture that has not yet burned)
so more time for that mixture to ignite spontaneously.
The surface area also becomes larger, so more heat is absorbed.

I think you shouldn't see it as 1 2 3 4 5, but more as 1-2-4-8-16-32.

I have no experience tuning 4-strokes, but there are similarities with a 2-stroke.
End gas is when the mixture has not yet been reached by the flame,
but is already being compressed and heated.
Due to that pressure and temperature, spontaneous combustion can occur (detonation).

I would look for the solution in that squish gap, because if there is good mixing of the mixture due to a powerful squish flow, there is less chance of end gas detonating. More squish velocity = better combustion, and a narrow squish gap cools the end gas located there.

Personally, I find that my Savage cylinder gets very hot.
My intuition tells me that tuning can cause problems, especially if the diameter increases.
Lowering the compression might be a solution and an easy option. When I look at the Dipsidoedel in the exhaust channel, which looks like the Strait of Hormuz. Then I think the exhaust side gets much hotter than the intake side, more so than is the case with other engine brands.

So the combustion dynamics in the combustion chamber must be optimal, and the carburetor and ignition settings also require closer attention. Making sure you don't inhale hot air from the engine can also help.

Just my two cents, Bless you. learned a lot from this tread.