Assuming you've got a 3-way mechanical fuel shut-off, start it and immediately start pulling back on the shut-off slowly bypassing fuel back to the tank. Idle will increase and temp will too, so don't pull back too far, but 15-20 seconds or so should clean out most gunk buildup, Definitely a trial and error method, better to lean too slowly than too quickly.

BTW the crystals form in old alky, top lube won't help there