Curt
There’s not nearly enough info out there on it. Basically its a FR-125 engine with a different cylinder that delivers more power than the standard FR-125. It also has a two speed gear box with an ignition intrupt so you do not have to lift when shifting (but it is advised that you lift). The axle goes through the gear box so it does not have a chain. The clutch is an internal centrifical wet clutch so clutch life is much longer. The gear box is basically a high/low affair.
You do have the usual DelOrto carb so you do have to jet the thing. The gearing is high enough that on top, it should be just as fast or faster than most shifters. You gain a low speed range to yank the thing out of corners.
The main things it has going for it is that’s it fast, almost as fast as a full blown shifter. It is very low maintenance, the engines last at least 50 hours. There has yet to be a single reported failure of the engine due to a bent axle. I’ve looked at the internals and the axle is very well supported inside the engine. (better than a any current designed kart) There is no chain to maintain and no oil related mess.
Retail price of the engine is just under $3,500 and that is a very complete package including radiator, battery and pipe. The only thing needed in addition is the mount and a kart. A complete package is around $7,500. At Ocala, the DD2 were about .6 second quicker than the internationals.