Can a food processor base/motor that is used during the year/chometz be used on Pesach if the bowl and blades are new?
Yes, but it should be cleaned well with a cleanser (ammonia etc.) and if possible, pour hot water over it.
Ashrei Ish 3 pg 353, in the name of R’ Eliyashiv. See Ohr L’tzion 3-10 ftnt. 9, that one should not use the base of a mixer that was used for flour etc. because the flour gets into the motor and it can fall out on to the pesach counter.