Okay too much theory also not very good... let us see something practical today...

From post #2, i did mentioned that rear drive system is the way to go therefore some engine modification required.

Many first generation castings on DLE111cc rear crankcase is having the slot for RNA4901 needle roller bearing. This particular bearing is suitable for the application since it has a very high axial load capability. With installation of this bearing DLE also created 4 lubrication slots surrounding it's casing (these slots can be viewed in the first picture). Since we want to extend the crankshaft for the starter drive system therefore some work need to be done on this area.

First step is to remove the bearing. Then using lathe machine, we re-bore just enough to remove the lubrication channel. While the unit still on the lathe machine, we drill a center hole (16.2mm) on the crankcase. Machine an aluminum bush similar to the size that has been removed via maching, press fit this bushing. Then we do some shopping.... hehehehe... we get ourselves the RNA4901.2RS bearing. This bearing is having same loading capability but with something extra, it has lip seals at both ends. This will prevent crankcase leak. And due to this seal also, the bearing typically will be having some pre-packed grease on it's rollers therefore no further lubrication required. Press fit this bearing onto the bushing.

Refer sequence of pictures below.