Supplemental Instruction that comes with the #217960 – X7 Formula Kit, the instruction should be in the kits with the main gear/washer parts.
First, keep in mind the most important issue to resolve is proper 66T Crown gear mesh adjustment with the 14T Tail transmission gear.
This should be very smooth running and the main purpose for adjusting main gear gap.
One should adjust the upper gap of the 66T Crown gear and the bevel front tail transmission gear first.
To do this follow the below procedures.
Start first with W12.1x17x1.2 washer on top of main gear, then fill the bottom of the main gear with some washers to fill the gap in the bottom.
THEN add/or reduce with other size washers to adjust proper gear mesh between the 66T Crown Gear and 14T tail transmission gear.
*For example if you started with 1.2mm Washer as recommended and feel too tight the gear mesh between 66T & 14T.
THEN you should add a 0.2mm washer to increase the mesh gap slightly.
If it is too loose the 66T & 14T gear mesh, then you should remove the 1.2mm and use other smaller washers to achieve proper gear mesh
(reduce washer on top to be less than 1.2mm by using a combination of 0.2mm and 0.3mm washers to be 1.1mm or 1.0mm etc….
When the TOP (66T & 14T gear mesh is properly adjusted).
THEN make sure the bottom of the main gear there is no gap with adjustment washers.
Then tighten everything, you’re done.