Originally Posted by LukasM
Please add some pros and cons to your choice in regards to the criteria stated above.
Ahhhh I thought we were just having a brainstorming session
Well, The pros of the 800 engine are known, think of an overbuilt dr650 engine. In terms of consumption I doubt it is as bad as you rate the dr650. With standard gearing on motorway doing an indicated 140 it returns about 7lts/100km if jetted properly. The gearbox ratio is 3.0 which is not too bad.
The cons are weight, it weighs about 60kgrs.
Having said all that, I think the most fun engine you could have is probaby that of the versys, but I'm not sure how easy it is to fit due to width. As far as single cylinder engines go, the 800 is the dog's bollocks. A guy here in greece has fitted it in a yz450 frame for the supermto championship. There is a thread here in advrider with some pics of it.
And a completely of the wall idea I have seen done in both an xt600 frame and an lc4 frame. A bmw boxer airhead 800.