I have never seen a chart but there may be one out there. Where all the confusion was for myself years ago was with gas engines. With glow engines a .91 two stroke is the same in either two or four stroke but with a gas engine a 2.4 is a 40cc engine. It's either 2.4 cubic inches or 40cc so you just need a conversion chart. I have a couple I found on line. cc is just cubic centimeters or metric and the 2.4 is cubic inch displacement and used in the US. .91 cid, 1.20cid. Without my conversion chart I would only know a few myself off the top of my head. The US is the only country I can think of that doesn't use the metric system. We gave it a try but all the older folks went a bit nuts trying it. It was given up and now most of us old farts that learned the metric system in the 60s can't remember it.