One of my trials bikes ( non battery ) generates the spark via the alternator via a 6 volt coil, points and condenser. The bike is not running but I have a bright blue spark. I suspect I have no spark when the plug is fitted and under compression. It has been suggested that a large blue spark is wrong and something may be breaking down. I have heard of plugs not sparking under compression in the past but cannot find any reference to this. All fuel aspects and compression are fine. I know there will be a few experts on here, thank you.
