Bikes can be really bad noise wise, radios even when powered by their own battery can have a hard time.
You could try powering the circuit from its own 12v supply, with just the gnd connected to the bike (all other inputs unplugged) and see if the circuit runs with the bike running.
You might need a low pass filter on the input to the 7805.
Some smaller engine bikes can have several volts of noise on them, that would uspet a pic but not neccesarily blow one up.
The supply to the 62783 is confusing, you've shown a transistor shorting out the lm317 with its base powring the 62783, its marked up link, is this a link or a tranny, if its a link is it fitted properly?