Posted by Willy-N on Friday, May 07, 2004 at 0:19AM :
In Reply to: Re: One more question!?!?! posted by Willy-N on Thursday, May 06, 2004 at 11:54PM :
This explains what I am tring to say about not firing under compression but firing out side the block.
High Voltage
Air is not a good conductor of electricity. In the atmosphere, a spark of 12,000 volts can jump a gap of .025”. Under pressure, like in a cylinder, it is harder for the spark to jump the gap. The pressure inside the cylinder of a two-cycle engine, like a chainsaw, outboard, and simple snowmachine, is about seven times greater than our atmosphere.
A spark plug that can spark in the open air may not be sparking at all in the cylinder. It took me three days to learn this as I cranked and cranked on a motorcycle.
The strength of the spark is revealed in the color. A red or yellow spark is weak and probably will not spark in the cylinder. A blue or white spark is strong and has enough voltage to fight across the spark plug gap even under pressure within the cylinder.
Reasons for Spark Plugs Not Igniting Fuel
There are two main reasons that a spark plug will not fire well if the voltage is present for a good spark.
The gap is not set properly.
There is carbon on the plug, shorting it out.