Originally Posted by nella
My question is should I make a breather arrangement for my plug? If so, why does the gear box need to be vented?
Yes you need a breather. The 'box contains air and oil that expand as it is heated causing an increase in pressure in the 'box. The temp of the gearbox can vary quite a lot from sub zero to ( guessing here) 80 C.
Without a breather to vent this pressure, it will be trying to get out of the seals and either finding its way into the clutch, or the shaft, or down onto the road.