hey, thanks for the comments.
working in white overalls is the bomb, you always look completely greasy, like you've done heaps of work, even if you haven't
the engine is a chinese pocket bike engine (49cc or possible 47 or even 40cc, either way, it seems to have enough power) and it comes with the centrifugal clutch, the exhaust is also from a pocket bike, although modified to fit this application. the cool thing about the motor is all the aftermarket upgrades like head kits to up displacement and compression, timing keys, reeds, carbs etc..
here's some more pics...
this shows the sprocket welded onto the original pedal end, this way, if i want to remove the shaft i can take out the retaining pin and just pull the sprocket off and then pull the shaft out the other side (that's right, pull the shaft, hehe) on the other side, there is a piece of pipe welded to extend the axle and then a little metal plate welded to that. unfortunately i didn't line it up straight, oh well, so then the sprocket is held on my 3 screws that have rubber washers in between the plate and the sprocket, which you then tighten to get the sprocket spinning straight...it's not too bad, althought the sprocket moves around slightly which means that the chain goes from being very taught to very slack. i'm thinking of either extending the holes in the metal plate to be slots so that i can bolt it in dead central, or getting a chain tensioner that is kindof spring mounted so that it always keeps the chain tight. what do you guys suggest? as currently the chain falls off under hard revs.
here's a shot from the other side
here's the exhaust