Magneto Cam

Harry B.

Petty Officer 2nd Class
Joined
Oct 11, 2007
Messages
101
I have a 1968 Johnson 20 hp.
I'm trying to set the points and am having some malfunction. I can get one side gapped great, however the other side.....well, not so good of luck.

Could the magneto cam be worn out on that side. Do magneto cams wear out???
 

samo_ott

Vice Admiral
Joined
Jun 18, 2006
Messages
5,125
Re: Magneto Cam

Are they new points? What happens on the other side? Why cant you set them? I've never heard of, or seen a worn cam... But I guess it could happen...
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Re: Magneto Cam

I have a 1968 Johnson 20 hp.
I'm trying to set the points and am having some malfunction. I can get one side gapped great, however the other side.....well, not so good of luck.

Could the magneto cam be worn out on that side. Do magneto cams wear out???

Ain't no way the cam could be worn out on "that side". "That side" is the same side that opens the first set of points. You rotate the shaft so "that side" comes around to open the second set. In other words, rotate the shaft till a set of points is open as far as it will, then adjust the gap to .020". Rotate the shaft 180 degrees and repeat with the other set.
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: Magneto Cam

Set the points at .020 with the fiber rider portion of the cam rider aligned with the crankshaft keyway. Only way they won't set correctly is if the armature plate itself is worn and sloppy...
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Magneto Cam

(Magneto Armature Plate)
(J. Reeves)

If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns.

The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make an indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.

You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.

Use a small amount of anti corrosive grease between the aluminum ring and the brass support plate and also on the brass bushing of the armature plate when all is well.

(Point Setting Of Magneto Models)
(J. Reeves)

Set the points as follows. Have the flywheel key aligned with the fiber rubber portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

NOTE: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.
 
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