1976 Harley 36v - Voltage Spike when first accelerating

[ryanfast]

I have a 1976 Harley Davidson 36v golf cart and have been trying to hook up headlights. I got a set of 12v headlights and hooked up a 36v to 12v reducer. The reducer seems to work well (13v'ish when testing with a multimeter on the out from the reducer), but there appears to be a power surge when initially stepping on the accelerator. The headlights work fine, but when I accelerated the bulbs blew (I must have too large a fuse since it didn't pop the fuse). I hooked up the multimeter to see what it read when accelerating and when it clicks to engage the motor the volts jump way up (30+ volts). Is there anything I can do to stop the surge that is burning out the lights / would pop the fuse? Thanks!