ORIGINAL: gkamysz
The more powerful you make the magnet the stronger the attraction when it passes the magneto. This means the flywheel needs to be stronger. An axial arrangement only makes this worse. To strengthen it you make the flywheel deeper, this of course increases weight so now you are machining it to make it light again. Machining is not cheap no matter where you do it. Somebody really needs to look at the cost of actually making one.
It looks like some of the Zenoah engines have relatively small diameter magnetos. Are these not made specifically for the RC market? Why aren't they smaller?
The problem with the Zenoah mag is they need a coil also, and that small rotor looks lite...but weighs more than you think. It is compact though. Capt,n