First,welcome to the engine conversion hysteria.I hope your dad has lots of room somwhere if this hits you like it has so many of us.Anyway,The 2 pics with the flywheel are 21cc echos.your engine should look somwhat close to this engine so you get an idea of what to cut off.DO NOT CUTOFF THE PART THAT HOLDS THE COIL ON!only cut off around it that isnt being used.I cut off the fins from the flywheel.if youd like your flywheel converted for you Ken from lambertsrc can do this as make mufflers and so does Pete from wackerengines.ive only delt with these 2 although there are more.just search here on RCU.The other pic is of a converted 23.6 echo with a battery cdi.i dont suggest this type for your first one though.your only going to loose about 6-8 ounces and its not that much difference when you put it on a stick or somthing with a good wing area.this engine needs a good plane with wing area and low wing loading.just ask away and we will help.