Hi Rollmyown,

I'm not the designer, or anything to do with the engine manufacturer (its used in a few different brand names) I was just interested when it came out as its a bit different, so I found out why and how it works. You probably already know this but the throttle bore to the reeds is air only, all air/fuel mix goes through the other barrel and direct to the crankcase. The reeds are only open for a very short time, the idea being a fresh air charge leads the air/fuel mix into the cylinder so the air only charge follows the exhuast gases out, so no unburt hydrocarbdons exit the exhaust. As soon as the pressure from the crankcase forces the air/fuel up the transfers it closes the reeds and allows air/fuel into the cylinder. I've got some images but its on my PC at work, I might be able to post them up next week.

Hope that makes sense, its a very well though out engine and well made, just a shame they did it for emissions not performance! What we need is a 12000rpm trimmer engine LOL.

Cheers,
Rich