Spark plug gap

[tlg1100]

Just put on new green dyna coils,old ones lasted over 20 years still using old dyna s ingnition and have been running stock plugs and stock gap. Is that right or does dyna suggest different gap?

[Flatline_Racing]

.034 seems to come up often with regards to the dyna s and 3ohm coils

[trippivot]

.028 is stock

dyns S = .026

dyna 4000 .018

these values come from a greg cope tuning tricks located at the APE gs zone tech tips link.

[rapidray]

What Trip said! Ray.

[tkent02]

Why a smaller gap than stock when there is a more powerful spark? Wouldn't it have a bigger spark and thus more efficient burning with a larger gap? Or would it start to break up at uber high RPM?
Not arguing with the experts, I just want to understand.

[Carter Turk]

I've had mine at .035 for 10 years, is that bad or stupid or both? A local bike mechanic suggested it years ago, but when confronted recently, claimed he never said that. He explained flame propagation would be bigger with a wider gap, which seemed to logically make sense at the time.

The bike hasn't let me down yet, but wondering if the performance is suffering with that much gap.

[gearhead13]

I had mine gapped at 35 for a while. The bike had a stumble/misfire at certain higher rpms. I almost drove myself nuts thinking it was a jetting issue. I regapped them to .026 and it runs much better
Thats with Dyna S, Dyna green coils, coil relay mod etc.

[trippivot]

smaller gap requires less time for the coils to re-saturate. which is the term for the coil to have a fully charged electromagnetic field to collapse and snap a little blue spark as the ground is taken away from the coil by the ignition module. Technically the lower the primary resistance the higher RPM's the coil can operate at. 3 ohm work great up to 10K and blue .7 work above 12K rpm

a very un efficient combustion chamber needs more advance or a bigger spark . like a huge piston dome or a crooked path from intake over the piston around to the exhaust valve ( briggs flat head design for example). . ALL OF the suzuki 2 valve hemis or 4 valve TSCC engines have a VERY EFFICIENT environment for the flame front to create the downward force upon the piston.. therefore smaller gap and less advance.... racing chevys or Air Cooled volkswagens generally have 42~45 degrees full advance and 0.040 gaps. we get by with 38(2V) and 34 (4V) and run over 10K rpm.

and I like to mention the heat generated by a huge plug gap is not what we want either... to large of plug gap can and will ZAP AN IGNITION BOX. be careful if you are zapping spark for testing against the engine and it is over a quarter inch- half inch will get your finger or put the box into retirement.

[tkent02]

smaller gap requires less time for the coils to re-saturate. which is the term for the coil to have a fully charged electromagnetic field to collapse and snap a little blue spark as the ground is taken away from the coil by the ignition module. Technically the lower the primary resistance the higher RPM's the coil can operate at. 3 ohm work great up to 10K and blue .7 work above 12K rpm

a very un efficient combustion chamber needs more advance or a bigger spark . like a huge piston dome or a crooked path from intake over the piston around to the exhaust valve ( briggs flat head design for example). . ALL OF the suzuki 2 valve hemis or 4 valve TSCC engines have a VERY EFFICIENT environment for the flame front to create the downward force upon the piston.. therefore smaller gap and less advance.... racing chevys or Air Cooled volkswagens generally have 42~45 degrees full advance and 0.040 gaps. we get by with 38(2V) and 34 (4V) and run over 10K rpm.

and I like to mention the heat generated by a huge plug gap is not what we want either... to large of plug gap can and will ZAP AN IGNITION BOX. be careful if you are zapping spark for testing against the engine and it is over a quarter inch- half inch will get your finger or put the box into retirement.

Good stuff, thanks!

[goggleboy]

and I like to mention the heat generated by a huge plug gap is not what we want either... to large of plug gap can and will ZAP AN IGNITION BOX. be careful if you are zapping spark for testing against the engine and it is over a quarter inch- half inch will get your finger or put the box into retirement.

dang. I remember when I first bolted on my dyna 3ohm coils and a purple spark jumped from the end of the spark plug wire to the park plug over an inch away....

[Carter Turk]

So a .28 gap on a 1229 with 3 ohm dyna's is fine?

Some folks have probably already seen this, it's shot inside the combustion chamber.

http://video.google.com/videoplay?docid=-5815350492893860613&hl=en

[tlg1100]

thanks for the info been running stock setting for some time