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ignition question


HumanFireHazard's Avatar
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08-23-03, 10:57 AM   #1  
HumanFireHazard
ignition question

hello... what is that igniton stuff under the flywheel? how can u ajust timing with that? and plz some explain to me how does it work? is it like capacitor that says charged and it lets it out to the spark plug whne the mechanism clicks?

 
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08-23-03, 07:06 PM   #2  
engine ear
if you see a plastic looking block-like thing with a piece of metal and a wire sticking out of it then you identified the ignition coil. i'm not sure as to how you would adjust it. On the flywheel there is a magnet imbedded in it and on the opposite side there is a counterweight. when the magnet passes the ignition coil it sends a high voltage shock throught the wire that goes into the spark plug. the spark is then dissipated through the body or chassis of the motor.

 
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08-23-03, 08:34 PM   #3  
Hello HumanFireHazard!

The points on old engines are commonly found under the flywheel (most models). They can be adjusted to affect timing. The coil air gap can also be adjusted. (B&S air gap is .010", points gap is .020").


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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08-23-03, 09:15 PM   #4  
HumanFireHazard
so what does that thing under the flywheel do?

does it cut the coil form the plug? i see that the crank has a lome in it... that pushes the pin and contacts the round cyclinder under the flywheel...

 
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08-24-03, 05:13 AM   #5  
mikejmerritt
Hello HumanFireHazard, this is why we are all thankful for electronic igniton.....

From LMRM......
This is the procedure for setting ignition timing on old Tecumseh's with points under the flywheel. Tools required.

1. Ohm meter or some sort of test light for checking continuity.
2. .020" feeler gauge.
3.
--A. Dial indicator with proper offset adaptor, or
--B. A fine ruled measure stick and straight edge.
4. Misc. hand tools.
------------------------------------------------

1. If using the proper dial indicator, remove the spark plug. If using a measure stick and straight edge, remove the head and clean the block surface.

2. Clean points or install new points (new points should be cleaned as well). Find the high point of the lobe which activates the point arm. Some will have a small arrow (not to be confused with some lobes having a set of lines). Rotate the crank until the high point is at the point arm and set point gap to .020".

3.
--A. Rotate crank until piston is at TDC with both valves closed. If using a dial indicator, from flywheel side, rotate crank counter clockwise 1/8 turn. Install dial indicator. Adjust indicator so the probe is into the bore. Slowly rotate crank clockwise until piston contacts indicator probe. Continue rotating clockwise until dial stops turning (you're back to TDC). Zero the dial. Then rotate crank clounter clockwise until the piston is at your engines BTDC plus .010". Example. If you're engines BTDC timing is .090", go to .100". Then very slowly turn the engine clockwise until at your engines BTDC figure. In this example, .090".
--B. Measure stick and straight edge. Basically the same principle here except you'll be laying the straight edge across the cylinder bore and using the measure stick to find your engines BTDC timing point.

4. OK. Make sure the crank position is not moved. Loosen the stator plate so it can be rotated back and forth, not sloppy loose but enough you can move it freely. If not already, disconnect condensor and kill wires from the point terminal. Connect ohm meter or continuity tester, one lead to the point terminal, one to engine block. Rotate the stator plate clockwise until the continuity tester or ohm meter shows continuity, points closed. Then rotate stator plate counter clockwise very slowly until continuity is broken, points just cracked open. If all has been done right, you can now tighten the stator plate and reassemble engine.

If the point activation lobe has a set of lines, spaced about the distance that equals the width of the point arm that contacts it, the lines and point arm should center. If not, you want to find where you went wrong. Often as not, error is made in the point gap itself. If all else seems to be correct with the actual stator timing, reset the point gap using the lobe lines and point arm centering them as the moment the points crack open on the continuity tester.

 
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08-24-03, 10:54 AM   #6  
HumanFireHazard
I dont want to be rude... but could some one asnwer my question... WHAT DOES THE THING UNDER THE FLYWHEEL DO?
how does it set the timing? how can i retard timing?

 
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08-24-03, 12:48 PM   #7  
mikejmerritt
Just Be Calm...LOL....

I can see that it would be helpful if you new that the ignition stuff under the flywheel is a coil (commonly called a magneto or stator), points and condensor. All of this is mounted to a plate that can be moved to alter timing. The instructions in my last post explain how to adjust this system. You would have to understand how to set the timing as the factory would before you can retard or advance the timing. You have it right on about the condensor (round cylinder as you call it) holding a charge, it really is a capacitor. If you really want to know the details of the firing system do a google.com search for keywords magneto, coil, stator and points. You will find all you need to know.

If you need more details on your engine post what it is....Mike

 
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08-24-03, 06:45 PM   #8  
HumanFireHazard
ok thanks man... cool.. il do a search.. now i know what it is called... condensor... k... so basicly... the coil gets energy like on a compressing stoke and release when needed? when does the condensor get charged?

 
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08-24-03, 09:08 PM   #9  
There is a magnet on the flywheel. This magnet goes past the pickup legs on the magneto (part with the plug wire coming out of it). When the magnet passes it, it creates a magneticl field in the small wire windings in the magneto. Then, the lobe on the crankshaft allows the points to close, which grounds the ground wire on the magneto. This allows the magnetic field to collapse out of the magneto. There is a core in the center of the coil/magneto that the plug wire is connected to. When the field collapses, it sends a high voltage pulse out the core and through the spark plug wire to the plug, causing the spark. The condenser controlls the speed of this release from the coil. Then, as the engine turns, the points open back up, the magnet passes the magneto again, build up the field again, and so on.

"how does it set the timing?"
It doesn't set the timing, it just creates the spark. Setting the timing requires moving the magneto.

"how can i retard timing?"
Opening the point gap slightly, or rotating the magneto clockwise can retard the timing somewhat.

Hopefully this gives you the understanding you are looking for.

Is there a problem you are trying to figure out? If this is a tecumseh engine (by the sound of this thread, it is), it is best to never move the magneto unless necessary. They can be a pain to get set back right without the proper tools.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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