This discussion on spark color is far different than we believed in the age of old magneto and points and coil ignition systems . Modern systems like BTH devices show little color and nearly invisable spark yet will punch through a sheet of paper leaving a hole. Indeed the older equipment showed a icy blue bolt at its best , orangey second rate and thin white when needing work . At least so it seemed to us . I still believe those old indicators . The Hamon system was seen to jump damn near two inches of pure blue lightning bolt if you wernt careful with it , with a sharp crack to be heard . Explain the differances between it and other modern systems please . Sid . .
Poor starting on new Amal and BTH Magneto
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More on spark . I believe a good Victor breaker on a hot Comet and on a twin a Series D dist . and a first rate coil and fresh condenser will do the job , gas or methanol on high compression without failure . But needs external power of course . Sid .
My experiance with the drag bike on gas , 9to 1 , 32mm TTs . A std magneto . This worked well but as I developed the motor further it began to miss fire . Then I changed over to a Series D Dist driving a HD truck coil and twin 12v batteries . This worked perfectly , never dropping a beat . Development continued , going to 13to 1s on Methanol , 1& 3/8s inch GP 2s. Still superb , then full kit with 2 inch inlet Big port heads , twin fronts . Still on the high domed Specilloid pistons , long ram tubes . Went its fastest and quickest , still on the 12 v Dist system . This certainly had heavy cylinder pressure and still the D system never faltered .
Very easy starting , one hard single paced lunge and drop the clutch , bang . Perfectly Consistant . Trouble free . I did switch over to wet cells , cheaper not continuely buying new dry cells , that got stale . Sid .
Very easy starting , one hard single paced lunge and drop the clutch , bang . Perfectly Consistant . Trouble free . I did switch over to wet cells , cheaper not continuely buying new dry cells , that got stale . Sid .
If you were too far advanced and certainly as much as mentioned above you would get a serious kick back from the kick starter, if not this ain't the prob.
The earthing idea sounds a possibility but never heard of a "high frequency spark" being invisible before, I have and have had electronic ignition on BMW's and believe me the spark is quite visible! don't touch it whatever you do as it will hurt!!. Try the earthing as this sounds like the prob.
The earthing idea sounds a possibility but never heard of a "high frequency spark" being invisible before, I have and have had electronic ignition on BMW's and believe me the spark is quite visible! don't touch it whatever you do as it will hurt!!. Try the earthing as this sounds like the prob.
Great stuff ! Our Gardner on the 600 single is a easy starter and ticks over quite nicely once the float height , needle position and the plastic line from float to body is the correct length . This is critical as the fuel lies in its loop , must not be too long .
Your choke will certainly cause lumpy running if left closed . It blocks off much of the air passage so must have that effect .
To clear the sump of too much fuel vapor lift the comp . Lever and spin her over a few times , the air draft dries out the excess and also the plug , do it with the throttle wide open for this effect . Sid
Your choke will certainly cause lumpy running if left closed . It blocks off much of the air passage so must have that effect .
To clear the sump of too much fuel vapor lift the comp . Lever and spin her over a few times , the air draft dries out the excess and also the plug , do it with the throttle wide open for this effect . Sid
On maximum advance for greatest power , this always was the most important point to get right even tho the engines needs varied , today it's clear that the act of starting is far more important for us old geezers and old motors too . This needs be closely observed to occur at 4-7 degrees BTDC . On today's gas one seems better off to retard the max advance , it to be reduced a bit . Originally called for at 39 degrees BTDC on the comp. stroke , now 34 / 35 , even less .
As the motor starts on full retard on ADT equipped machines this ensures sufficient pressure against the piston to carry it over and down the power stroke forcefully enough to sustain an idle . Sid .
As the motor starts on full retard on ADT equipped machines this ensures sufficient pressure against the piston to carry it over and down the power stroke forcefully enough to sustain an idle . Sid .
I think the Briggs and Stratten spark advice was valid in their day and when dealing with their simple ignition systems , these on par with original British equipment of 60 years ago . They built millions of stout little motors that often ran for decades , must have known something , this in dust and damp with little service .
Their spark tester , had one since a lad and still use it . A clear plastic block with two pointed electrodes buried in it , some considerable distance apart . The spark was clearly visable , color and width . Great fun to use . The plug cable slips on and there's a spring clamp allowing it to grip a fin , provide a perfect ground . All is revealed clear as we're it out in the open . Sid .
Their spark tester , had one since a lad and still use it . A clear plastic block with two pointed electrodes buried in it , some considerable distance apart . The spark was clearly visable , color and width . Great fun to use . The plug cable slips on and there's a spring clamp allowing it to grip a fin , provide a perfect ground . All is revealed clear as we're it out in the open . Sid .
I noticed this thread a few days ago but have restrained myself from commenting. As you might expect given the strong demands for greater fuel economy and lower emissions, the properties of spark ignition have been intensively studied, and all aspects are quite well understood. Unfortunately, they are not well understood by most magazine writers and web sites, so much misinformation circulates.
Spark ignition has a lot of aspects to it, and so any accurate description of it must be fairly complicated and technical. However, in what follows, I'm going to simplify (even greatly simplify) the processes, and make direct connection to what a proper understanding means for ignition systems for our motorcycles. Taking something easy first:
What should have been said is that a magneto must produce a spark that will jump a 5mm gap (i.e. 10x the gap of a spark plug) at room pressure in order that it have sufficient voltage to jump the 0.018" (1/2 mm) gap at the ~150 psi in the combustion chamber. In other words, if you don't see a spark across a plug at room pressure you definitely have a faulty magneto, but even if you do it tells you nothing about whether the magneto will start the engine.
This is nonsense. Here's a greatly simplified description of what goes on when a spark ignites ignition:
--Within a few hundred microseconds or less the voltage across the plug has risen to a high enough value for things to start happening.
--Free electrons in the gap between the electrodes are drawn toward the positive electrode, colliding with oxygen, nitrogen, and fuel molecules and liberating more electrons that also are attracted to the positive electodes. At the same time the positive ions that have been created by the loss of electrons are drawn toward the negative electrode, also colliding with other molecules along the way.
--When the positive ions hit the negative electrode electrons are released, which travel toward the positive electrode. The motion of these electrons/ions creates an ever growing cascade.
--Within a small fraction of a microsecond after all of the above starts the instantaneous current in the channel where all of this is happening has reached several hundred Amps, which is called "breakdown."
--The conversion of electrical energy to kinetic energy of the molecules is very efficient, resulting in temperatures over 50,000 C in the channel. This is actually too high for the formation of stable chemical reactions, but the temperature also causes a shock wave to form. At the leading edge of the shock wave the temperatures are lower, so chemical reactions are initiated with the oxygen (and nitrogen) and the fuel molecules, energy is released, and a flame is initiated which will continue to grow if the shock wave has exceeded the threshhold needed to get a self-sustaining chemical reaction going.
--Meanwhile, ions are continuously created by the collisions, and are continuously lost as well as they capture free electrons. When an electron is captured, the excess energy is given off in the form of light of very specific wavelengths (colors) determined by the chemical constituents (oxygen, nitrogen, OH, and the various hydrocarbon segments) and the laws of atomic physics. That is, there aren't "hot ultraviolet" vs. "cool blue" sparks.
--A minimum energy of ~0.5 mJ from the magneto is required to create a shock wave of sufficient magnitude to cause enough heat to be released by oxidation of the fuel to keep the reaction going.
--However, although only ~0.5 mJ is needed, this is a case of more being better. The initial flame created is fragile and can be extinguished by the turbulence in the combustion chamber. The more electrical energy that is dumped, the greater the shock wave channel, and the more robust the initial flame.
If your ignition system is producing a spark in the air that seems weak, it is weak. It's not because your particular type of ignition system is producing an "ultraviolet" spark, it's because it isn't depositing as much energy into the ionized channel as some other type of ignition system. The color of the spark is determined by the chemical species present. In the case of a simple test across a spark plug in your garage, those chemicals are almost entirely oxygen and nitrogen (the 'click' you hear is the shock wave). They're the same independent of the ignition source. However, while the color is the same, the brightness is proportional to the total energy produced by your spark system. Brighter is better. No, let me modify that. Brighter is a lot better.
Think I'm at last getting it thanks to you guys . I might add in that it seems to me that the wider gap at the plug holds back the discharge , and in that longer moment more pressure is built up and the intensity increased , seen when it does jump as a stronger spark .
Put another way , the Lucas D Dist . calls for a gap of 28 thou , a mag only 18 . If you reduce the D gap to 18 the advantage seems to to be reduced . The wider gap forces the electrical pressure to increase .
Your thoughts ? Sid .
Put another way , the Lucas D Dist . calls for a gap of 28 thou , a mag only 18 . If you reduce the D gap to 18 the advantage seems to to be reduced . The wider gap forces the electrical pressure to increase .
Your thoughts ? Sid .