RE: Black Spark plug= what
spark plugs are the other way round to glows, black is to rich, what oil mix are you running? 25:1? 30:1? ect, you might not be mixing enough oil with your fuel which may cause you to not see the smoke, generally you will see it though even without much oil (speaking from motocross bikes here, i havn't had any experience with large scale rc's, but i assume them both being high performance two stroke engines to have similar characteristics with the oil mix)