I think your code is cycling the motor when you are holding the button down.
Pseudo code
//Cycle 1
Spintime is 0 so
it calls the first block
turns motor on and
sets Spintime to 1
//Cycle 2
Spintime is 1 (not 0) so
it calls the second block
turns motor off and
set Spintime to 0
Every 250 milliseconds it flips the motor from on to off then back to on. On / Off / On / Off
The Spintime variable is not latching and essentially running your motor at 1/2 speed.
Shameless plug: On/off switchable motor - #13 by Hudsonville_Robotics