0.4 to 0.5 is a high start value, so expect some flames as the engine transitions to normal fuel. remember that the kero start is only pre-heating the combustion chamber, imagine a gas start engine with a pump start voltage that high, its a bar-b-que ! i would encourage you to (if th engine is in the airframe ) make a closed loop in the fuel system, by putting the line that enters the engine back into the fill valve and hold the pump test button on for a total of 40 - 60 minutes, then check / adjust the pumps start voltage, and / or temporarly install an on/off tap after solenoid and before the engine, and only allow a dribble of fuel in on start. be careful of allowing 0.5 worth of fuel in at start-up, especially if its in the airframe. you may not burn it, but the pipe will certainly not appreciate it