Tard farm here we come....

The air gap in a spark plug can't exactly be modeled with a resistor like mach1 says.  A lot of things just don't seem to add up.  By your claim, the voltage across the electrodes is only ~12v.   

While yes, when the arc occurs between the electrodes, there is current flowing as the air ionizes and the circuit is completed, but it's really the high voltage that is necessary to get it to ionize in the first place.  And the strength of the air gap as the dielectric increases with the bigger gap, so a higher voltage is needed to start the arc.

http://wiki.answers.com/Q/Can_back_EMF_be_greater_than_battery_EMF

        Here for general knowledge :
http://auto.howstuffworks.com/ignition-system2.htm

To the OP , if you want better spark buy iridium spark plugs,more expensive but last much longer

New coils are 80$ each 

This thread = fun.

Inductance, capacatance, resistance.  Watt's a matta; you no obey Ohm's law!  You could be king faraday.   

prs

I didn't expect my topic would spark (literally!) so much interest. 

The best test would be to disconnect one cylinder, revv-up the engine and see/hear. Then repeat the same with the other cylinder. If no missing occures then the gap mod is in fact working, though outside of the design specs for GS500.

The effects of a larger gap are unlikely to be obvious from the start and the method you suggest wont account for the long term degredation of the plugs.
To make an accurate comparison and avoid the placebo effect you would need to take two identical bikes, fit one with standard gap plugs as a control and another one with oversize gaps. Dyno, fuel consumption and emission test them both. Run them both for say....... 1k, assuming the bike with oversized plugs makes it! over similar conditions then repeat the tests and compare the differences.

Quote from: sledge on June 29, 2009, 01:29:46 PM
The effects of a larger gap are unlikely to be obvious from the start and the method you suggest wont account for the long term degredation of the plugs.
To make an accurate comparison and avoid the placebo effect you would need to take two identical bikes, fit one with standard gap plugs as a control and another one with oversize gaps. Dyno, fuel consumption and emission test them both. Run them both for say....... 1k, assuming the bike with oversized plugs makes it! over similar conditions then repeat the tests and compare the differences.

I was talking about the mod viability check, not about obtaining some scientific numbers on the performance differences. I have no time nor second GS500 to perform all that noncense.

If GS500 does not misfire or burn parts as a result of the mod, it means it is viable. By how much it improves the bike performance? Who knows.. Theoretically there is a stronger spark, so there is some performance improvement.

People do far crazier mods to their bikes.  

OK opening the gap causes increase in resistance. The spark may not jump at low revs. But once the voltage hits the jump point it should be fine. It will cause a drop in current, because V/R is current.
BTW the low voltage side of the coil is not 12 V from the battery, its 15-75 volts AC from the alternator. I cannot see it ever losing high speed. I believe low revs first will die. I would really not worry, we throw in resistor plugs in the things all the time. My virago runs better with resistor plugs than regular BS plugs.
Cool.
Buddha.

This thread is going so far, ahem, afield!

When the bike is running there is about 15 volts on line, DC.  Everything on the bike runs on DC, after the rectifier.  And sure, the spark is current, but it takes thousands of volts to make it begin, and that's why an engine with too large spark plug gaps will begin missing at some point.  And it isn't so much the energy of one spark that determines if the coil can keep up, it's the increasing energy needed as rpms increase as there's less time between sparks, increasing coil and ignition module load, since the module controls the coils.  The ignition module and coils are actually seeing a greater load of the larger plug gaps more often with increasing rpms.

And a hotter spark isn't always better.  If that was the case, mechanical ignitions would work better than electronic ignition as mechanical ignition delivers full coil power to the plug every time as it can't regulate spark current.  Electronic ignition does regulate spark current, delivering enough spark current for the engine load, but no more.  That's why plugs last longer with electronic ignition over the old points and condenser, like I have in my old 77 XS 750 triple, with three sets of points.

So to summarize, all increasing the plug gap does on this bike is increase the load on the coils and ignition module.  Sledge and I are correct.  Argue with us at your peril.  I'm not looking to pick fights on issues like this or anything else.  I have an electonics degree and 27 years of experience.  I'm here to shed light and disperse myths.  Japanese engineers are smart on these issues.   You don't see them playing with plug gaps, do you?  They selected the ignition coils and module for your bike with the recommended gap for good reasons.  If you can successfully outguess a team of Japanese electrical engineers you're a better man than me.  It's all about covering the rpm limits of this engine with parts that are up to the job.  They selected them.  They left the specs alone for 20 years.  What does that tell you?  You can observe it or suffer the consequences.

Quote from: bill14224 on June 29, 2009, 05:28:44 PM
.... You don't see them playing with plug gaps, do you?  They selected the ignition coils and module for your bike with the recommended gap for good reasons.  If you can successfully outguess a team of Japanese electrical engineers you're a better man than me.  It's all about covering the rpm limits of this engine with parts that are up to the job.  They selected them.  They left the specs alone for 20 years.  What does that tell you?  You can observe it or suffer the consequences.

That is all correct, however we all know that longevity/problem-free-product/budget considerations put a lot of strain on the designers. Companies (at least Japanese LOL) want to produce dependable long-lasting machines, but at times at the expense of performance (obviously except race-oriented ones). Nothing's wrong with that. They try to design machines performing well in a wide variety of situations. God bless them. GS500 is one example. Simple, dependable, archaic, cheap, unintimidating.

But we are exploring and tinkering with the design, often obtaining better-than-designed parameters. Examples? Igniton advancer. Smaller front sproket. Braided brake lines. Wider rear tire. Katana shock. Progressive springs. Rejetting. Etc, etc, etc. This board is choke full of those ideas. God bless it.

More spark is better, it's a fact. Otherwise some modern engines would not have two spark plugs per cylinder.


You see where I am driving to?

Peace.
P.S. I will ride with my enlarged spark gap, just to give you guys some feedback in a year or two. You stay as you are. Nothing's wrong with that. That's how the humans progress. Some go ahead and take risk. Some stay back and wait. Nothing's wrong with either. I've used somebody's experience countless times doing the mods others explored before me. I am thankful they took the chance (and the risk) to light my way.

Reminor - Yes I will await your observational postings.

Bill14224 - The jap companies have/had 2-3 phases.

In the 70's and 80's they were out to take over the world. They built solid machines that ran and ran and ran ... not extrordinarily grat in any respect but not too horrible in any other aspect. In that phase they were very hard to improve upon. They fixed their problems themselves. Example - early virago'/s starter problems. Gone in 1984. 81-83 bad, 84 on was great. Maxim's had transmission problems. Again second gen maxim fixed. List is endless.

Then came the "why aren't you buying more parts from us phase" The virago became the Vstar - yes not one of the problems was fixed, and many were made harder and worse. Virago of 84+ once in a while will eat a ignition box. The new Vstar - it still eats it, but its now encased in tar. Much harder to get out and fix. The oil change on a Virago is a 1/2 hour job. You ahve to remove the case guards to get the filter out. Vstar - that + removing the exhuast which is much much harder than a GS - think collector box under the motor and its shoved in there tight. Plus they added a few nice ones just to catch ones that are sleeping - rear spark plug - near impossible to not cross thread on the way in, and hard as heck to get a wrench on on the way out. Open shaft, that really really likes to rust. Once again, coat it with oil or it will look like the ... well forks.

Agreed GS is more form the first phase and we can only make small improvements - as opposed to huge en masse changes and I think this is worth trying out. especially on my damn virago.
Cool.
Buddha.

Here's my update after over 250 miles on the spark plugs with enlarged gap. I measured the gap and it is 1.05mm (stock is 0.8mm) on both plugs. Take a look at the picture. The plaugs had over 2k miles on them before the mod. I think they look good. The bike runs perfectly.

Well, I just had to put in my 2c....
Plug gaps are probably specified by Suzuki a little on the small side of the ideal, so that as they wear they don't get too big. It also would mean that people who don't check their plugs often enough aren't bad mouthing the bike for misfiring. So, if the spec is 0.8mm I guess the ideal gap is maybe 0.9 or 1.0. If you enlarge the gap a little and check it frequently I suggest you would probably have no problem, but I doubt you'd see any noticeable gain in performance.

As for the larger gap 'overloading' the coils, I call .
Yes, if the voltage is only JUST ENOUGH to get a spark and the gap is made  larger you will need more voltage to get a spark. That does NOT mean the coil will magically produce more voltage. The coil can't 'know' how big the gap is and adjust its voltage accordingly.  It just means that if the voltage it is already producing is not enough then you won't get a spark.
In fact, there is more than enough voltage for the normal gap, so if the gap is a little bigger it still works.

(Ducks behind sandbags and waits for incoming rain of used sparkplugs!)

Let him carry on with the exercise, no one said anything would happen short term.

There is an effect of larger plug gaps, I felt I should chime in. I remember a while ago when switching our old 1988 Honda Accord to splitfire plugs. It idled roughly and stumbled a little bit at low revs. Turns out the more exposed electrode actually advanced the timing a little bit which isn't detrimental at higher rpms since normal ecu's advance timing at higher rpms naturally but at lower rpms it can cause problems such as higher cylinder head temps and stumbling or even knocking. There is a slight delay between when the plug fires and creates a small fireball in the spark area to when that fireball spreads and ignites the fuel-air mixture. A larger gap does expose more mixture and even though it is not a hotter spark it is a larger fireball in the immediate spark plug area, and has the effect of advancing the timing, which possibly accounts for why the op feels there is a slight difference as advancing the timing manually can have an effect.

As to the long term effects I would later be concerned with misfiring later on down the line. You're probably not going to end up damaging the coils but there is a possibility, if there was a small manufacturing defect or damage in the coil's insulation repeated misfiring could end up burning through the weak spot in the coil's insulation and you end up with a coil that grounds to itself. A rare occurrence but a possibility nonetheless.

Just an FYI 101 on ignition to spark plug:

Ionization of the gap is the good start to begin the flame kernel development. And that requires a certain voltage level at a certain amperage level. The width of the gap, and the turbulence and pressures in the combustiion chamber greatly affect what those voltage and amperage values have to be; or what they need to be. The ignition coil has to be able to supply the required voltage at the needed amperage flow, as quickly as it can, once it has been triggered to do so. That is known as 'rise time'.

Once the ignition coil has produced and delivered that required voltage pressure and amperage flow to jump the gap across the plug electrodes, the spark commences. In other words, the ignition coil is triggered, the magnetic field collapses, the induction of high secondary voltage commences [voltage rising], and the gap is starting to tingle in anticipation [ionize] for what is coming real soon. When the spark actually completes the jump, the ionization is complete: we have a spark.

The width of the gap has its effects on the quality and the intensity [heat] of the flame kernel that develops as the spark is sizzling across the gap. A wider gap will require more voltage/amperage to make the spark actually happen, so that can be a good thing. If you can jump the gap, that means that you had to have some heat there to get it to happen.

I was reading the topic about fixing the cold blooded nature of a GS by increasing the valve gap and it got me thinking about this thread. I wonder whatever happened to that bike.

Hi reminor  are you running low octane fuel in your bike or is the brown colour from your normal running .Could you post a better picture of the earth electrode a side on view would be nice.