You should be able to slightly rock the spur, try this in several spots with out moving the pinion.
Another way is to put a cigarette paper between the spur and pinion and just move the pinion up to the spur and tighten motor mounts, then just rotate the paper out and it should be the perfect mesh.
I just do my first suggestion & never have any probs with mesh issues.
FT TC4, LRP TC Sphere, LRP X-11 13.5
M03M Suzuki Swift
Power by Feral
Sanwa MX-3 FHSS