Setting the points

David Toll

Reliving my youth?
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Fired my '78 up and she was running OK but I had done this on the spur of the moment and I knew that I needed to check and set the points gap and timing. Excellent articles and videos here for that job and I assumed, with it running so sweetly, it would all be a cinch. Doesn't quite appear to be the case. Got all set to go with AJS drivers and feeler gauges and rotated the motor anti-clockwise......... no gap opens in the points!? Attempted the same thing in a clockwise direction and still no gap. After 10 mins of this I decided to seek advice in the manual. The book says that new points, (these are), still have to be cleaned and adjusted. I assume this means that you have to find the rotational point where the points themselves open up in response to the lobe on the cam and then set the gap at this. I loosened the set screw and opened up a random gap, tightened the screw down, rotated the motor and, yes, the gap opens and closes around this spot. They seem to stay open for a long while but I have never done this before so I don't know what to expect. Did the same with the left hand set. I checked with my circuit tester just to see if there was power to the points when the gap was open and there was. I now intend to go back and set the gap to 14 thou. then set the timing.
Is this approach OK? I am worried that there was originally no gap but my bike was running beautifully. I am also worried about the random establishment of the initial gap and whether this will interfere, in some way, with the timing. The old girl was running well but, I am keeping the points so I have to familiarise myself with the set up or buy a bike trailer.
 
welcome to old school ! Stay at it, It gets real good. ;)
Two tools I use and recommend as helpful are : a solid tight non ratcheting breaker bar with the 17mm socket for firm accurate control of engine rotation. That or plugs out in 2nd gear..
By chance do you have the factory gap setting blades in your tool kit pocket ? Smaller than feeler gauges and much easier to fit into the points area.
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Its a great learned skill to have! Cheering you on for success. It will take a few tries to have both cylinders timed. It is rewarding in the end.
-R
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If using feller gauges to set the points make sure you clean them with carb spray or brake clean before using. Do not touch the end of the feeler gauge with your fingers. Any oil residue on the contacts will cause the points to burn prematurely. Best shop I ever worked in the owner insisted you set them by eye and then checked with a dwell meter. If you want to test the coil stick a feeler gauge between the points with the key on. Learned the hard way.
 
Hello Jim
Yes, I have poured over that video but, he begins by rotating the motor and the points opened up. Mine didn't do that, they stayed together. It wasn't until I loosened the gap adjusting screw and opened a gap that I was able to rotate the motor and have the points open and close. I have opened a gap in this fashion on both sets of points and have now gone back and gauged them to 014". I am about to do a static check on the timing with a circuit tester light. Just a little unsure if this is the correct way to go about it as nothing I have watched or read prepares me for points that did not open when rotated. Obviously, the lobe on the points cam pushes upon the fingers on the moveable points arm and forces the points to open. I am assuming that this was not adjusted at the factory and, hence, the new points didn't open as I rotated the motor. Possible?
 
I am assuming that this was not adjusted at the factory and, hence, the new points didn't open as I rotated the motor. Possible?
When you install points, the default setting will be closed because of the spring tension closing them. If the new points were installed with the lobe at it's highest lift, then as you rotate the lobe off it's peak, the points will remain closed. I suspect that's what happened. Sounds like you're on the right track now.
 
This is a great skill to put in your repertoire and can be applied to any old bike or car with points.
Points are just a switch that applies and cuts power to the coils. I think of it like this: when points are closed the coils charge, when they open that charge is “released” through the plug wire to jump the plug gap.
They have to open and close to make spark. When they are open, they have to cut the ground to the coil, when they close they have to make electrical contact and provide a ground path to the coil. I’ve seen many point sets that look like they close but are burned or corroded and not actually making good contact to provide the ground path to the coil thus not charging up the coil to be able to release the spark.
And they have to open at the exact right time (ignition timing)
The little fiber block that follows the points cam wears down. This will diminish the gap and make the spark happen later and later (retarding timing) as it wears. Eventually, without adjustment, the points stop opening and the charge/release cycle stops happening and no more spark.
So first you have to reset the max gap, the point where the switch is most fully opened by the cam. The timing is the moment when tips of the points just (Electrically, best shown by a 12 volt test light) break open, cut the power to the coil and release the spark to the plug.
Very cool, very simple. And the condenser is just an electrical shock absorber that keeps the points from sparking excessively and burning quickly. But they can short out too basically overriding the points and making them act closed all the time.
The concept on electronic ignitions is the same. Power to coils cycled on and off to charge and release the spark.
Just no mechanical wearable parts to adjust and replace. Done by magnets and sensors and black box voodoo.
All that said, a point ignition should survive an EMP better than electronic iggys.
The choice of end times preppers everywhere!
Hope this helps!
 
OK, I have set the gap at its widest point on the compression stroke. I placed a thumb over the plug hole and felt the build up of pressure. I continued to rotate the motor util the gap in the points was at its widest. I set the gap at 14 thou. I then hooked up the test light to check timing. The light comes on well before the first "F" line. . I would have assumed that it was advanced. It stays on for some time after I have passed the "F" marks but the video shows it coming on at the first mark and going off after the second mark - mine appears to be "on" for too long. Opinions?
 
It stays on for some time after I have passed the "F" marks but the video shows it coming on at the first mark and going off after the second mark - mine appears to be "on" for too long. Opinions?
No, the light will stay on until the points close. That's quiet a few degrees of rotation past the second mark. If you have your 14 thou gap at the widest opening, you're halfway there. Now you just need to adjust the plates to time it so they open on the F mark.
 
OK David, just reread what you wrote....
" I have set the gap at its widest point on the compression stroke. I placed a thumb over the plug hole and felt the build up of pressure. I continued to rotate the motor util the gap in the points was at its widest."
The points will not be at their widest point on the compression stroke. In fact, they will be closed on the compression stroke. They should stay closed on compression until about 15° before you reach TDC on the compression stroke. Once they open, continue to rotate past TDC and the gap will continue to widen until it reaches its widest point towards the bottom of the power stroke.
 
You're right, of course, Jim. I have misread Too Many's earlier post,
"The raised ridge goes to the rear. To be sure left/right timing is set correctly, pull right plug, put finger over hole, rotate engine until you feel pressure, you are coming on the compression stroke for right side. Right side point should be closed here. Continue rotate engine until rotor mark is in 'fire' zone. Right side point should just start break here... "(June 1 2013)
Will try it again the correct way.
 
Yes, the points remain open for quite some time. The dwell value for these is 93°. The dwell is the time during one 360° rotation of the engine that the points are closed, or "dwell" in the closed position. 93 is about 1/4 of 360 so that means the points are open the rest of the time, about 3/4 of a revolution.

If you're serious about keeping the points, you may want to find yourself a dwell meter. It is the best and most accurate way to set your points gaps. It measures them electronically so there's no chance of measuring errors like with a feeler gauge. Also, no chance of fouling the points surfaces with oil from a feeler gauge because you don't use one anymore.
 
Showing your age there Steve. Fortunately, I have a pack of Camel at hand - for auto-electrical purposes only you understand.
Take your point 5T and your explanation on dwell is short and clear. Shopping for dwell meters now - will try and get a meter/timing light combo.
Cheers
 
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