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Saturday, December 11, 2010
Timing a 1964 and older Harley Davidson Ironhead with Magneto
On 1964 and earlier (yours) models the magneto is mounted in a fixed position to produce advanced spark timing only. Later than 1964 the spark timing could be retarded for starting.
So live with the advanced timing as there is nothing you can do about it. Simpler system with less parts is the way to view it.
To set the ignition timing follow these steps:
Set the spark plug gap at .020 on each plug.
Remove the 4 screws and remove the Bakelite cap from the magneto.Set the points gap at .015. A note is in order here:
The ignition cam in the magneto has 2 lobes. The sharp lobe is for the front cylinder.
The wider rounded lobe is for the rear cylinder.
I always prefer to set the .015 gap with the sharp lobe (front cylinder) raising the points foot to open the points.
After doing that, rotate the engine forward and measure the gap at the other lobe (more rounded lobe-rear cylinder). This gap needs to be a maximum of .004 from that which you just set at .015.
Under .004 is better and more than .004 difference means you have a problem, which I will not get into here to keep this as simple as possible.
Next step.....Here we go......
There are 2 bolts on the base of the magneto that hold it in place. Loosen both bolts so the mag can be rotated clockwise and counterclockwise.
Next, remove the plug for the timing hole on the left side of the engine, located just below the cylinder bases.
Next, collapse the pushrod cover of the front intake valve. Raise the cover up so you can see the lifter. (Hold the cover in place with a rubber band and a couple of bent paper clips.)
Next, Remove both spark plugs and raise the bike's rear wheel off the ground. Put the gearbox into 4th gear. We will be using the rear wheel to turn over the engine as it gives the best control. If you want to do this instead using the kick start lever, that will work too. Just not as much control. Either case though..... remove both spark plugs.
Next, rotate the engine forward slowly. Watch the front intake lifter. It will rise and then come down. When it has just hit bottom, the piston will now be coming up on the compression stroke.
Continue turning the engine very slowly (less that a half revolution) and watch the timing hole. You are looking for the slash mark to appear.
*Next, get that (slash) timing mark dead center in the hole. (See notation below)
Look at the base of the magneto and make sure the factory timing marks on the mag base and the case are lined up.
What you should see at this point is the narrow cam lobe (front cylinder) should be CCW from the point's foot, and the points should be 'just opening.' If they are clearly open more than 'just' or they are not open at all, then you need to rotate the magneto either CCW or CW. It is best to use a continuity light to see if the points are open. Then adjust the mag by rotating it so the light goes on/goes out.
In the old days before lights we used to use cellophane paper from a cigarette pack to determine when the points were starting to open. But the cellophane is about .002 inches thick so it was not accurate but it was all we had at the time.
If you want to use the light and need to know how to hook it up just ask and I can give you the instructions.
Now, if this procedure results in you not being able to rotate the mag far enough to obtain the 'just beginning to open' points, let me know. Or, if the mag's correct position leaves interference with the carb.
This can happen if the mag has been removed or slipped teeth etc. If your machine has been running then that will not be the case.
*Notation: Always rotate the engine in the forward direction. Do not go past the mark and then back up the engine to line up the mark.
You will need to rotate it fully forward and catch the next time the intake valve closes and the mark comes up to the center of the hole.
Hope this has been clear enough to understand. This is the way the timing is adjusted on a magneto equipped 1960 XLCH.
One final note on the mag:
Do not disturb the 3/8 inch safety air gap that is between the copper tabs on the mag and the Bakelite cover when it is in place. What I am trying to say here is do not bend these two tabs.
If the gap gets messed up, it will take a sacrifical cap to reset the 3/8 air inch gap correctly and I am betting you do not own a spare magneto cap..
Put the magneto cover back on, pushrod cover back in place, install both spark plugs, install the timing hole plug, and you should be set to go.
This was pinched from PinionGear on the HDForums. He has a easy way to understand the process involved