Quote:

Does the backlash gear hold tension on the camdrive gear chain. WHY??


The backlash gear is spring loaded to provide rearward pressure on the camshaft gears themselves. When the lobe approaches the tappet, more pressure is applied to the chain causing it to tighten due to the increased load of depressing the valve spring. Once the lobe has crossed it's apex, the valve spring pressure could force the cam to turn faster than the cam chain causing loose motion or slack. Essentially it buffers the naturally jerky motion created by camshaft operation by maintaining a more consistent pressure on the cam chain. It's a very nice little trick... by doing so they minimize the possiblities of the chain jumping off one of the gears and prolong the life of the chain.
At least that's the way I see it.