1974 25hp johnson points gap?

[D.G.]

what is the points gap on this motor? i've set them to 20 thou but the idle is very poor.

 

[JB]

Re: 1974 25hp johnson points gap?

.020" is correct, D.G.

What have you done with the carb? Have you tested the coils?

 

[D.G.]

Re: 1974 25hp johnson points gap?

i've taken apart the carburetor and cleaned it. and i've checked my coils and i get consistant blue spark from them. my points were set a about 12 thou and i had good idle but no top end. but now that i've set them at the required amount i have very poor idle but the same top end speed. now the top end speed might be resolved i just installed a new fuel pump. now i'm torn on if i should go back to the old point set or stay at 20 thou. (diaphrams in the fuel pump were very stretched and my primer bulb would never really get hard)

 

[dew2]

Re: 1974 25hp johnson points gap?

20 is correct,It should be right on top the flywheel,If I'm not mistaken' Did you check all fuel lines for air leaking in?

 

[kbait]

Re: 1974 25hp johnson points gap?

Check link/sync too.

 

[F_R]

Re: 1974 25hp johnson points gap?

Put a timing light on it and see if the spark is occuring (while running) when the timing mark on the flywheel aligns with the marks on the armature plate. If it does, the points are set correctly. If it doesn't, the points are not set correctly. Wider gap advances the timing, narrower gap retards the timing. (Check timing on both plugs).

"Timing" as applies here means not only in relation to piston position, but also to flywheel magnets-to-coil position. The correct way to set the points is with the special tool timing fixture. But .020" should be close.

 

[Joe Reeves]

Re: 1974 25hp johnson points gap?

The following procedure will get you extremely close to perfect if no timing light is available.

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

Set the points as follows. Have the flywheel key aligned with the fiber rubbing 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.

And if the armature plate (plate the points are attached to) has a wobble to it which would change the point setting as it rotates, the following will cure that problem.

(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.