yep.... Ive done over 50 mph on one of my bike running a ( Puch 70cc hi hi ) which is said to have the wrong angle squish band for these engines and Ive also had engines that will do 40 mph+ running ild style stock straight plug heads that dont have a squish band at all in them.
With theae little engines, rhe most common performance level that most will ever acheve will have liitle to nothing to do with whether or not they have "proper squish"
correct port timing, better balance of the crankshaft, free flowing exhaust (stock exhaust if used needs flange matched closely as possible the gasket and port) wa to much back pressure on exhaust kills the power and tip speed of these engines even when all else is in good order, correctly jetted carb and some minor port and piston work that will ensure a good free flow of furl mix in and exhaust out.
If stick exhaust is used I recommend adding extra holes in the end cap to allow exhaust to get out easier, Ive seen engines gain 5+mph and get the ability to pull hills that they would barely pull previous to adding extra holes, these engines need veey little back pressure to run good when all elae is right.
I want to emphasize the right PORT TIMING & CORRECT CARB JETTING.
No matter what someone does to their engine, if these two aspects aren't right, its never gonna live up to its potential.
A very bad crank balance is a big performance limiter also.
If someone has whats referred tp as the "half breed" engine geometry, no matter what head they use, the compression will always be on the low side unless they deck about .060" of the jug/cyl. port timing is weird on them also. rod marking ZAE50 is a quick identifier of these engines or used to be.
I never not once tested for (squish).....Lol bikes ran fine