Welp, a 555 with those small-value caps near it (c3, c2, c1) could certainly be an oscillator to generate a square wave.
There appears to be a pretty big inductor (the black rubber-jacketed cylinder between the two green electrolytic caps at left),
which could also be part of an oscillator circuit. Another reason you might have a 555 in a throttle
is making a PWM output to the track. In fact, PWM would almost make more sense because I don't see any transistor on that board
capable of carrying the track current (even "low" current like 250 mA). I still say we need to put that thing on a scope to
really know what it's doing.