I knew I could get generate a more powerful spark and bridge a larger spark plug gap (than stock) w/ my new Jaguar CDI and coil, so I tried it but it didn't help performance at all -it actually became worse and felt much more "governed" or boggy at top end the more I increased the gap. After testing a dozen gaps I finally settled on .031" as being the best gap even with a performance ignition. Try your own experiments with gapping to see what works best for you. Reduce spark plug gap = advance timing; Increase gap = retard timing. I think the poor performance I initially experienced may be for 2 reasons.
The first is that I was maladjusting optimal timing by increasing the gap further from how the ignition operated most efficiently, the second has to do with spark plug design. Increasing the gap too much creates a new low point (spark pathway) on the side electrode which is now back closer to where the side electrode is welded to the plug than at the tip (end) of the side electrode. The spark fires earlier on the electrode pathway and then becomes more smothered and moves away from the center of the combustion chamber and is less efficient. Let the ergonomics (natural lateral space or invisible line of reference between the ground and side electrode of the plug itself dictate the best gap for that plug to make sure the lowest point is just barely at the very tip of the side electrode and draw that spark out to the very tip before it can fire a more effective flame front directed in the middle of the combustion chamber.
Most times this gap falls perfectly within recommended specs because this is very close to the pre-gapped distance. However, I've never met a spark plug that was perfectly "pre-gapped" for my specific application. After all, who's application are they talking about? There are hundreds of applications for each plug, all with different optimal gap requirements. You have to check each one and gap accordingly to find the sweet spot (mentioned above) because my experience is that there is always gap variation within the same box of plugs. Also, the side electrodes are often welded crooked so that the side electrode is not perfectly covering the ground electrode but is off to the side. I bend these with a needle-nose pliers so they are perfectly and evening covering the ground electrode and are not biased to firing on one side or another. Even better is to ask the store employee to let you open and inspect each plug before you buy.
Experiment with heat ranges 1 above and 1 below the recommended range long enough to see which one you prefer. I did this and found that the NGK BP6HS heat range that is always recommended performed worse than the BP5HS.
Finally indexing. I'm not sure this matters as much on small, relatively low-performance engines..Draw a line on the white ceramic insulator of the plug which is in line with the open area of the spark gap. Orient this open area of the gap in the direction of the oncoming fuel/air charge when fully screwed in. This can be done by adding or subtracting indexing spark plug washers (which for some reason are nearly impossible to find these days - anywhere)
The first is that I was maladjusting optimal timing by increasing the gap further from how the ignition operated most efficiently, the second has to do with spark plug design. Increasing the gap too much creates a new low point (spark pathway) on the side electrode which is now back closer to where the side electrode is welded to the plug than at the tip (end) of the side electrode. The spark fires earlier on the electrode pathway and then becomes more smothered and moves away from the center of the combustion chamber and is less efficient. Let the ergonomics (natural lateral space or invisible line of reference between the ground and side electrode of the plug itself dictate the best gap for that plug to make sure the lowest point is just barely at the very tip of the side electrode and draw that spark out to the very tip before it can fire a more effective flame front directed in the middle of the combustion chamber.
Most times this gap falls perfectly within recommended specs because this is very close to the pre-gapped distance. However, I've never met a spark plug that was perfectly "pre-gapped" for my specific application. After all, who's application are they talking about? There are hundreds of applications for each plug, all with different optimal gap requirements. You have to check each one and gap accordingly to find the sweet spot (mentioned above) because my experience is that there is always gap variation within the same box of plugs. Also, the side electrodes are often welded crooked so that the side electrode is not perfectly covering the ground electrode but is off to the side. I bend these with a needle-nose pliers so they are perfectly and evening covering the ground electrode and are not biased to firing on one side or another. Even better is to ask the store employee to let you open and inspect each plug before you buy.
Experiment with heat ranges 1 above and 1 below the recommended range long enough to see which one you prefer. I did this and found that the NGK BP6HS heat range that is always recommended performed worse than the BP5HS.
Finally indexing. I'm not sure this matters as much on small, relatively low-performance engines..Draw a line on the white ceramic insulator of the plug which is in line with the open area of the spark gap. Orient this open area of the gap in the direction of the oncoming fuel/air charge when fully screwed in. This can be done by adding or subtracting indexing spark plug washers (which for some reason are nearly impossible to find these days - anywhere)
