I always was interested on how these small engines work and the art of tailoring an engine powerband to conditions.We all know tuned pipes do that,but how about unleashing more power?
That leads me to engine timings and all the complications.There's really much to read and understand but the tip is Port area x time and this is where it gets too deep for me.First I'm showing my test subject,a SH PT12R02SXT.Standard engine like a NS12T1,not much power but from my measurements has so-so timings.Will be adding more pics and measurements today.Disclaimer,I'm not responsible for any damage you do on your engines.It's just my experience through what is available on various threads.
Specs: 13.8mm bore X 14.0 stroke 1.35hp @ 34000rpm slide carb standard plug.25mm rod with 4.0mm big end and 3.0mm smaller end.
Exhaust 82.5º for a 5.1mm port height;
Inlet 61.6º for a 2.9mm port height.
-inlet around 9.00mm
-exhaust 11.70mm widest part
Not measured yet,should be 29 open ABDC to 61.5 closed from TDC
7mm inner bore,non turbo.
Inner diameter:6.75mm(BTW 7.00mm is maximum by rules)
-bearing to bearing around 26.90mm
Crank pin length 4.57mm
Intake bore 5.45mm
Bore vs Stroke vs Displacement