Dyna iggy..run hotter?

The only time more spark energy, or more spark duration, makes a motor run better is if the mixture is off, or the engine is not designed properly, or is in really poor condition. Normally, with a proper mixture/engine, the flame front will spread fast enough such that for a given spark gap, any extended spark duration will be arcing through gases that are already burning, or have already burned. This is for any reasonable amount of spark. If you go to extremely short duration or extremely low current, you might start to notice a difference.

If you increase the spark gap by large amount, you are creating a much larger flame kernel to begin with, so you might feel a difference then. (But this puts a lot of stress on the wires, coils, and igniter.) You can also get faster burn by using two plugs in a cylinder. But these changes may require a slightly delayed ignition timing to prevent knocking in extreme cases. (Not detonation, or preignition, but simple knocking.)

So for Dyna S versus points, you would probably only notice a difference if the points were not working properly in the first place, or if the motor is in poor condition, or if the mixture is off. (All Kz motors fall into the category of "properly designed", for this discussion.)

Zed1015 put it nicely.

BTW, if we are talking about a 1978 or 1979 or maybe 1980 Kz650, you may want to do some searches regarding the charging system and Dyna S. Some (definitely not all) of those bikes have reported the Dyna S loads down the charging to where the battery gets drained over time. There may have been a batch of weaker stators for those years.

The biggest practical everyday benefit of electronic ignition is better starting brought about by the ability to use higher voltage coils and a larger plug gaps which give less likelihood of plugs get fouled with fuel. This also often gives a better idle. There are benefits when up and running like better fuel consumption etc. but mostly they will be too small to notice, unless the ignition is compensating for things like the mixture and carbs being off, by not allowing the engine to bog and misfire when too much fuel gets in there.

The other advantage after ease of starting, is a proper advance curve set by the electronics, as opposed to relying on the somewhat "all or nothing" spring loaded mechanical advance units, unfortunately we don't get that with most of the aftermarket systems which seem primarily to get rid of the points, which are always blamed for being far more troublesome than they really are. Having the ignition timing always set perfectly for every eventuality will bring benefits in driveability, power and fuel consumption, this doesn't happen with the mechanical advance, where full advance will be hit at around 2500-3000 rpm but even then worn parts and springs can make things more arbitrary.

650ed wrote: Maybe I'm wrong, but I would think if an engine has an air/fuel mixture under compression and a spark lights it off so it begins to burn the air/fuel will all burn or else be pushed through the exhaust system if not completely burned. I don't understand how a "hotter" spark is going to make more air/fuel mixture burn than a less hot spark. In other words, I would think that since the spark is only a momentary event, and that event ignites the air/fuel mixture which then burns to completion on its own, then any spark that ignites the mixture will burn the same amount of mixture since the spark is not a continuous event that lasts until the last bit of air/fuel mixture is burned.

That is 100% correct. Incomplete fuel burning is actually due to the fact that not all of the fuel oxidzes "properly" into a combustible form so a certain percentage remains unburned. That's what burns in the CAT converter of a car or flies out the tailpipe on a bike. Improving the combustion dynamics can actually get a slight improvement in how much fuel gets radicalized into the burnable form which is why wizards who know how to tweak intake manifolds and valve design can squeeze a bit more power out of an engine.

The ignition spark has to be really crappy before it gets bad enough that it is losing power due to that.

KZB2 650 wrote: 35,000 volts vs 15,000...... and since our bikes have a wasted spark system with less time to recover I will always run the Dyna's even though its may not be as big of a deal as it sounds.

The voltage claim is misleading. The OPEN CIRCUIT voltage of the electronic ignitions is higher but in actual usage, that almost never matters. The spark plug clamps the voltage when it fires. In other words, the voltage builds up until it jumps the air gap at which point it empties the stored energy in the coil. The only time that voltage can get up near the limits is if the plug is fouled or oil coated so it can't fire. The higher open circuit voltage means it might be able to come closer to firing a fouled plug, but good plugs don't need anywhere near the max voltage to fire.

redhawk4 wrote: The biggest practical everyday benefit of electronic ignition is better starting brought about by the ability to use higher voltage coils and a larger plug gaps which give less likelihood of plugs get fouled with fuel. .

I have not seen any convincing evidence wider gaps help. I have CDI on mine and have not seen any difference. However, running them wide does force the spark to fire at a higher voltage which stresses the coil winding more and probably shortens the coil's life.

redhawk4 wrote: The other advantage after ease of starting, is a proper advance curve set by the electronics,

I think that's true, no question dialing that in does maximize power and efficiency that a mechanical advancer can not do.

I've played with plug gap, and if your ignition system can handle large changes in gap, you will notice performance differences. Logically, it makes sense. If you double the initial flame kernel, the burn will spread faster. At high rpm this may be desired, but at mid rpm, you might get some knock (mechanical advance comes all in too soon). If the ignition can't hang, then might lose spark altogether. It's risky to double the gap, but easy to test if you are willing to sacrifice some coils and igniter.

I remember reading in a bike mag or two that increasing plug gap from .028 - .032 to .037 might give you a "little " power boost with the big coils....and did it for a while. Never seen much so I went back to .032.

.032 is the service limit.
Steve

I tried them a shade wide like .036 and it did nothing so I stick with the manual spec which is .032.