Plug gap?
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Joined: Jul 2008
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From: southeast PA
The gap makes a difference, but there is some leeway, usually +/- a couple thousandths. I'm surprised the one on the right is firing at all. Those plugs are not spendy, get a new set and gap them correctly.
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From: Honah Lee
Fi bike would tell you if it was missing. There's enough fire there with modern electronics it does not matter. Gap it correctly for long service..
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Welcome from Hampton Roads Virginia, USA!
Just in case you have not done both of these two important items!
Be sure to add an Avatar of your favorite shot in the USER set up for the small picture others will see in the top left corner of your post with your USER name.
And most importantly a Signature Line in your USER set up for your bike model, year, and all the letters that Harley recognizes it with that others see at the bottom.
This enables others to know your exact model if you ever ask a question or another member interested in it may ask you a question about it.
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ignitions of today is not like of old.
most are mediocre at best unlike the ford high energy system that could easily kill due to the long duration of the spark nor the gm hei ignitions which could inflict a nasty shock but being a short duration probably not kill. the reason behind this is back when, a coil must fire every plug but the norm now is a coil for every plug. this frees up some time for coil recovery/saturation.
an efi computer can tell you a problem cyl but not the actual cause as many things can cause a misfire, truth told, not every cyl fires every time.
i doubt seriously that todays norm is 70k but around 40k. truth told, most plugs fire around 8k so there is plenty of room.
gap matters no matter what. if you examine ignitions on an o-scope you will see the diff and every ign has its own signature.
if you stress the coil by large gaps, you stand the chance of over-heat or insulation piercing. also of note is that the coil also has a ring back that can stress the driver in the ignition system. in the ole points sys, the capacitor recovered this energy and sent it through again, today, the diode sends it to ground. this makes sure the coil can spark at the highest energy level as a saturated coil draws less current and it is the abrupt stop of current that induces the magnetic field collapse and spark. also of note, most coils today are auto-coils which do not have a primary side and secondary side per say, just one long coil with a tap.
most are mediocre at best unlike the ford high energy system that could easily kill due to the long duration of the spark nor the gm hei ignitions which could inflict a nasty shock but being a short duration probably not kill. the reason behind this is back when, a coil must fire every plug but the norm now is a coil for every plug. this frees up some time for coil recovery/saturation.
an efi computer can tell you a problem cyl but not the actual cause as many things can cause a misfire, truth told, not every cyl fires every time.
i doubt seriously that todays norm is 70k but around 40k. truth told, most plugs fire around 8k so there is plenty of room.
gap matters no matter what. if you examine ignitions on an o-scope you will see the diff and every ign has its own signature.
if you stress the coil by large gaps, you stand the chance of over-heat or insulation piercing. also of note is that the coil also has a ring back that can stress the driver in the ignition system. in the ole points sys, the capacitor recovered this energy and sent it through again, today, the diode sends it to ground. this makes sure the coil can spark at the highest energy level as a saturated coil draws less current and it is the abrupt stop of current that induces the magnetic field collapse and spark. also of note, most coils today are auto-coils which do not have a primary side and secondary side per say, just one long coil with a tap.
Last edited by bustert; Jun 19, 2021 at 08:58 AM. Reason: typos
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Seasoned HDF Member
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From: Poolville
Higher compression will make a difference in determining plug gap and better performance. Scott has told me as seen on a Dyno that .038" works very well without stressing the coil...
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Well there ya have it. Right there in black and white on the the internet...
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