sparkling plugs

alan hodge · Jul 27, 2018

well today I cheated a bit and took tag off 68 BSA A65 and put on 72/73 Commando 850 project/rebuild/construction (see 'It Lives' on this forum) and I went up the road for a couple of miles 'shakedown'..came home and made list of touchup stuff..fuel tap slight leak, gas tank rubs yoke at front, need better battery tiedown instead of zipties, recheck exhaust nuts..go over every nut and bolt..that's about it...bike started 2nd kick as it has since first startup last sunday...removed plugs after shakedown NGK BP7ES...and noticed they were a little dark...using Pazon Surefire/32mm Mikuni/KN filter...I use champion N4 in my BSA and Triumph T120 and they work perfectly...maybe use them in Commando? (I named it Uncle Sam because it was financed with my Social Security checks)...

htown16 · Jul 27, 2018

Nope, you need a projected tip plug. The P in BP on the NGK. If you want to use Champions use an N7YC. Y in this case indicating projected tip.

Onder · Jul 27, 2018

I am running the NGK with non extended tip, heat range as per standard. It is clean inside with black on the
circular portion of the plug body. Is not the extended tip to keep it clean? No problem with that as far as I can see.

Tornado · Jul 31, 2018

Does anyone "Index" their plugs? By this I mean determine where the electrode gap ends up facing towards when plug is fully threaded into head? Saw this described recently on Redline Norton's videos. Apparently, to adjust the gap side so it faces across the head, can be done by adjusting the plug crush washer thickness.

texasSlick · Jul 31, 2018

Tornado said:
Does anyone "Index" their plugs? By this I mean determine where the electrode gap ends up facing towards when plug is fully threaded into head? Saw this described recently on Redline Norton's videos. Apparently, to adjust the gap side so it faces across the head, can be done by adjusting the plug crush washer thickness.

There is some advantage to this?

Slick

baz · Jul 31, 2018

Tornado said:
Does anyone "Index" their plugs? By this I mean determine where the electrode gap ends up facing towards when plug is fully threaded into head? Saw this described recently on Redline Norton's videos. Apparently, to adjust the gap side so it faces across the head, can be done by adjusting the plug crush washer thickness.

Sadly yes I do this,I've never noticed any difference at all but I still do it!!

Tornado · Jul 31, 2018

The claim was the expanding flame front from the spark would not be interfered with as much by the electrode on its path across the cylinder head.

Here's the video at the pointy he started speaking of this concept:

Stillreel · Aug 1, 2018

Not sure I buy into this. The spark leaps from the electrode to the grounding tab to ignite the gaseous cloud mixture under compression. The resulting percussive explosion (rather than flame) would be instantaneously expansive in all directions, thus forcing the piston downward. I cannot see how a 1mm tab would have any effect in that environment. It would be like saying a twig could redirect a wave.

Just my thoughts.

Fast Eddie · Aug 1, 2018

I tried it in the past and could not detect any impact whatsoever.

Doesn’t mean there wasn’t any, just that I didn’t detect it !

Craig · Aug 1, 2018

“A butterfly flaps it’s wings in Beijing and it starts to rain in SanFran” Chaos , right ? ..... not sure I buy into plug indexing either .... some days I can only feel with my right hand , pretty sure I would never notice the improvement , plus it may well be time consuming in the setup .... to each his own , eh
Craig

Dances with Shrapnel · Aug 1, 2018

Tornado said:
Does anyone "Index" their plugs? By this I mean determine where the electrode gap ends up facing towards when plug is fully threaded into head? Saw this described recently on Redline Norton's videos. Apparently, to adjust the gap side so it faces across the head, can be done by adjusting the plug crush washer thickness.

I recall NASCAR and others do this (or did this). Not necessarily index to the orientation "you think" is best but index, dyno, index, dyno and on and on until you find (measure) the engines happy spot. Then index all plugs to that. I never did it and I don't know of anyone in the Vintage race arena that does this.

All this is getting eclipsed by Turbulent Jet Ignition.

Tornado · Aug 1, 2018

Ya, just one of those things somebody thought up once, happened to win a few races and everybody copied. Seen this effect in all types of competition...racing high performance sail boats the top guys had the fleet copying all their settings and adjustments...made no difference, top guys still won everytime...

Brooking 850 · Aug 1, 2018

I index mine out of habit.
Regards Mike

Nater_Potater · Aug 1, 2018

Tornado said:
Ya, just one of those things somebody thought up once, happened to win a few races and everybody copied. Seen this effect in all types of competition...racing high performance sail boats the top guys had the fleet copying all their settings and adjustments...made no difference, top guys still won everytime...

Likewise. It was one of those "racing secrets" in the '70s. We tried it for a bit with a circle-track car, but never realized any change. I joked with my newbie driver that if someone won a race with a Kachina doll hanging from the roll cage in the cockpit, the rest of the field would do the same the next race. There's still a lot of voodoo and black magic involved with racing...

Nathan

texasSlick · Aug 1, 2018

If the flame front propagates like a prairie grass fire, then the tang would "shade" the region directly "downstream" from the tang, which is the crux of the argument to index plugs. The hitch is ...... the flame front does not propagate like a prairie grass fire.

Combustion starts when an oxygen ion collides with a carbon or hydrogen ion, and if the collision has sufficient energy, then there is a reaction. The ions are randomly travelling in three dimensional space so the presence of the tang and its' position in space becomes mostly irrelevent.

I would relegate plug indexing to the status of voodoo magic, and I would be very surprised if anyone could show dyno data to support the concept.

Slick

xbacksideslider · Aug 2, 2018

Well said Slick but I believe in voodoo.

Could be confirmation bias but with Ducati singles when I needed everything I could get as I was running against two strokes, I methodically tested and refined a lot of stuff and one of my findings was that I got more out of a projected nose plug than I did out of a non-projected nose. No dyno, just bike to bike, day after day, rider to rider, coming out of that same corner, up that same hill, I got something.

Same argument applies - flame front propagation gets a head start if the plug's flame kernel is presented optimally to the fuel/air swirl.

Similar experience with a better ignition coil driving spark across a big gap with a platinum plug.

Could be that all these changes amounted to was an incremental advancing of the spark timing.

All that said, I can't say that I found an advantage in indexing by itself.

texasSlick · Aug 2, 2018

xbacksideslider said:
Could be confirmation bias but with Ducati singles when I needed everything I could get as I was running against two strokes, I methodically tested and refined a lot of stuff and one of my findings was that I got more out of a projected nose plug than I did out of a non-projected nose. No dyno, just bike to bike, day after day, rider to rider, coming out of that same corner, up that same hill, I got something.

Same argument applies - flame front propagation gets a head start if the plug's flame kernel is presented optimally to the fuel/air swirl.

Similar experience with a better ignition coil driving spark across a big gap with a platinum plug.

Could be that all these changes amounted to was an incremental advancing of the spark timing.

All that said, I can't say that I found an advantage in indexing by itself.

No question that a "fatter" spark, or two plugs gives a head start to combustion. Combustion starts in the spark track, which is like a miniature lightning bolt. Temperatures in the spark track, are like that in a lightening bolt, in the tens of thousands of degrees. This temperature is what dissociates the fuel molecule, and the diatomic oxygen molecules, producing the C+, H+, and O- ions that are necessary for the reaction of combustion.

Either a fatter spark or dual plugs produces a greater volume of high temperature space where a greater number of ions are produced, and are subsequently available for reaction. More ions at the instant of spark, means a head start for combustion. The result is, in effect, like advancing the timing.

Dual plugs and magnetos are used in piston powered aircraft engines. In pre-flight engine run-up, the mags are switched from dual to either left or right mag only, and a slight loss of rpm is generally observed on one mag, as compared to dual mags. This drop (generally 25 to 50 rpm) shows that dual sources of ignition results in more efficient combustion.

Slick

Fast Eddie · Aug 2, 2018

Iridium plugs, high out put coils, good leads. Anything that give a stronger, fatter spark will yield benefits in the old tech combustion chambers. That’s what my dyno testing has shown on several occasions.

I still don’t buy into indexing though!

BTW, mate once double plugged a racing Velo. It was a highly developed bike. Set to a fast tickover to warm it up, he noticed the revs drop on one plug and rise on two plugs. Evidence of mucho gains he thought...

But the dyno showed it actually produced less power! Clashing flame paths causing issues is all he could come up with as to why.

Onder · Aug 3, 2018

With aviation heads, the combustion chambers (and bores) are pretty big. A whole lot bigger than in a bike. Always figured it was to cause
combustion all over at the same time.
...the other thing is aviation is all about redundancy so having two plugs two mags etc was a safety thing perhaps.

sparkling plugs

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