neu motor and 18.97 speed control

[auto2]

i had a fine design junk motor 7xl with sultz 18.97 the motor went bad 3 times. each time all of a sudden it would just cog fully and not even move the buggy even in the air. each time a new motor fixed the problem.
this time I got a neu motor ( 4 pole?) from mike.
i still have the same problem as the old ( i thought was bad) 7xl. SO either the speed control took a dump or the 18.97 doesn't work or needs certain setting for the neu motor????