Bevel Gears 
Bevel Gears
I cannot find any pictures on the net similar to the unit I used on my earlier kart. I hope to take a photo of it and to put it here in this section. However I will explain how I went about using this "shaft drive" (with built in bevel gears, a crown wheel and pinion to be exact) to transfer the verticle rotation of my lawnmower engine to a horizontal one.
Once I obtained the actual part from a old motorbike 90cc which was a nice size, I set about putting the actual component into a frame which I could bolt to my engine easily. What I planned to have was the unit bolted rigidly to my engine, (combine the lawnmower engine and this unit into one power unit). From the final shaft out of this unit I planned to place a sprocket and from there I could transfer the now horizontal drive to my gear box or rear axle. It took a lot of messing around joining the input shaft of the bevel drive unit to the drive shaft of the engine. If I went to make it again I'd say it'd be totally different, i.e. there are no exact measurements I can give you, nor any steps to making the unit join to the lawnmower engine. Basically what you need is a bit of common sence and a bit of knowledge and a welder. For example one should realise that if the engine shaft is welded to the drive shaft of the bevel unit at a crazy angle and off setting, the connection will break and the vibrations would be unbareable. Basically when you are connecting two shafts:
1:. They must be perfectly in line. That means that there should be no angle between the two shafts or technically the angle should be 180 degrees.
2:. They must be concentric. This means that no matter what the diameters are the center of each shaft must match the center of the other shaft. If the shafts aren't concentric then the connection will wobble eventually breaking something and knocking any chain off it's sprocket.
Inside these "Right angled driven units". Basically any unit which has 1 shaft going into any gear unit and a second shaft comming out at right angles (90 degrees) to the first shaft can be used to adapt the drive from a lawnmower engine to suit a horizontal rear axle. I couldn't find any pictures showing complete units. Only what's inside these units.
THIS TO THE LEFT ARE "BEVEL GEARS".
THIS TO THE LEFT IS A "CROWN WHEEL AND PINION"