Fan balance

[Mike Sanders]

[QUOTE]In an ideal world we need as you say either a separate balancer shaft or another piston on the back side of the engine (longitudinal twin?), which then balances the engine internals.[/QUOTE]

The real answer is a horizontally opposed twin. The two pistons then balance each other out. They make them for planks, why not helis?

[KevDavies]

[QUOTE=Mike Sanders;998660]The real answer is a horizontally opposed twin. The two pistons then balance each other out. They make them for planks, why not helis?[/QUOTE]

ive seen these in big gassers [url=http://www.kingcobra.co.uk/engines/engines/pterodactyl-twin-72cc-pte72t.html]Pterodactyl Twin 72cc [PTE72T] - Engines - Engines[/url]

but your right mike a 90 twin would produce more power than a ys120 and being a twin no vibes either