<HTML>As far as sparks are concerned. Unfortunately it is near impossible to create a spark with two pieces of metal in this way. Remember, to get a spark in this way you need to really (and I mean REALLY) vigerously scrape the metal. But - - if you dont feel comfortable in this way, just use VERY clean rocks and maybe some solvant. However, the bolt and gas method has been used many times by many people, and I have yet to hear a horror story about anyone blowing themselves up with this method. I also in adition to using this method with a dirt bike gas tank, I also used the same method on a 29 model A gas tank which had almost 60 years of rust and corrosion in it. I am happy to report that 5 years later I am still alive, and the car is still runing well with a sparkeling clean sediment bowl.