i would change the spur as well
in my experence i've found the tamiya ones to soft, even a little peice of sand riped it up,and i was buying a new one after every race meet. i've since changed to using RW racing spurs and
they are much much better, i've had about 5 meets and heaps of pactice time and its still perfect. unless your running on carpet in which case it should be fine.
as for using a 0.4pitch spur with a 64pitch pinion, i don't really know but i've heard it works.
hope i've helped
