ORIGINAL: DarZeelon
As you lean the mixture; breaking from a definite four-cycle to a clean two-cycle mode, the engine will immediately gain 1,500-2,000 RPM.
If you lean it further to peak it, you will only gain about 500 RPM more, before the mixture becomes too lean.
This is typical in sport engines.
I know this is wandering off topic but hey...that happens all the time
Dar, I suspect you used that 1,500-2000 rev increase from your prop charts on the mistaken assumption that breaking into a 2 stroke doubles the HP. It doesn't.
So here's a hands on test I just finished. First, a Rossi 45 side exhaust with standard muffler gave me about a 500-800 rev rise from the highest speed I could say it was still 4 stroking to a point where the 4-2 break was virtually finished (just the very occasional 4 stroke hic). Further leaning gave an extra 2000 revs. Just for interest's sake (although I wasn't really trying) I had it growling nicely at about 5000 revs at full throttle
Next up was an OS 40VF with the pipe lengthened so it was just a huge muffler (well maybe, at the revs I was turning it could have tried getting on the pipe
). Almost exactly the same results as for the Rossi. I thought about trying it with a couple of my CL engines but that wouldn't have come under the heading of a typical sports engine.
To bring things slightly back on topic, I guess running them in wrong is one way to lower the compression