Do the open points cause the coil to charge and fire in that moment? (I can see the coil is grounded through the points when closed)
ANSWER: NOT EXACTLY BUT SOMETHING LIKE THAT: For the coil to develop high voltage across its secondary winding, its must FIRST draw current (when points are closed, they act as a current On/Off switch) and an electromagnetic field is developed. THEN when they open (CURRENT IS INTERRUPTED), that magnetic field collapses and induces a higher voltage into the secondary windings. i.e. the coil fires when the points break open AFTER they were first closed so the coil drew current and an electromagnetic field was developed which collapsed when current was interrupted.
QUESTION
And what of the gap? Why the critical nature of the point gap?
ANSWER: The gap determines in part how long the points were closed (to draw current to build up the sufficient magnetic field), its (dwell time) not any problem in older and say 2 or 4 or 6 cylinder engines at low RPM but if you had an 8 cylinder at fast RPM there could be issues with insufficient point closure times (dwell). Also, when they open a voltage develops across them and the gap has also to do with the arcing n sparking and arc extinguishing (that a word lol). They also have to be the right width to correspond to the rise from the cam lobes so they open to interrupt current but not so wide they dont close back fully when the cam height drops. The cam height and points gap plus the necessary dwell time plus the arcing are alllllll factors in proper points gap.
QUESTION
And if I may one more?
YES YOU MAY
What is the purpose of the condenser?
ANSWER; A primary function is to extend the life of the points by absorbing some of the current (that lil arc across points right when they break open) to reduce premature burning and deterioration of the nice silvery points coating. The coil will still fire if theres no condensor buttttttttttttt the points will burn up sooner PLUS the spark isnt as it would be if a proper sized condensor were present. Think of it as sort of a shock absorber analogy, it absorbs some of the shock (electrical current flow). Its size rating in microfards is also important as that sort of controls the rate of energy discharge when that magnetic field collapses. If the condensor is too big, theres no spark becasue theres not any rapid enough magnetic field collapse BUTTTTTT the points will sure last a long time as theres little current arcing across them. However if the condensor is too small the points will burn up rapidly although she will still spark, just weaker.
DISCLAIMER its impossible in a few sentences here to explain this vey well so this may be over simplified and NOT perfect or all 100% technically exact, but it ought to give you a basic idea. Read the stuff Scotty linked to and theres whole libraries on this subject and its impossible to cover here.
If you need, I have a canned troubleshooting procedure for non sparking I can post it if you wish, let me know
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Today's Featured Article - The Cletrac General GG and the BF Avery A - A Bit of History - by Mike Ballash. This article is a summary of what I have gathered up from various sources on the Gletrac General GG and the B. F. Avery model A tractors. I am quite sure that most of it is accurate. The General GG was made by the Cleveland Tractor Company (Cletrac) of Cleveland, Ohio. Originally the company was called the Cleveland Motor Plow Company which began in 1912, then the Cleveland Tractor Company (1917) and finally Cletrac.
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