Wico XH mag timing adjustment...

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MikeEyre74
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Zip Code: 06063

Wico XH mag timing adjustment...

Postby MikeEyre74 » Tue Apr 16, 2019 7:06 am

So my 1949 cub has a Wico XH magneto on it. It starts and runs fine and goes about its business without issue. When I broke out my timing light last night, I fired up the tractor and checked the timing and saw that it was off. I loosened up the bolt on the magneto and rotated it counterclockwise “Towards the engine” as seen while sitting in the drivers seat. You can only rotate one of these magnetos so far before the housing on the magneto hits the forward most bolt that holds the coolant hose adapter onto the block. I can take the magneto out and move it past that bolt to clear the corner of the magneto, but I suspect that the timing might be off in the other direction probably the same amount as it is now because I think right there at the corner of the magneto where the interference is, is where it is supposed to be. the IH J4 Mag must be physically more compact. As my Cub only has one timing mark on the pulley, I can only say that it is about 1/4 of an inch to 3/8ths of an inch away from being at the proper mark on the pulley according to the timing light. is that enough to bother with? I mean, it runs and all...

Eugene
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Re: Wico XH mag timing adjustment...

Postby Eugene » Tue Apr 16, 2019 9:50 am

Check the timing at engine cranking speed without starting the engine. Adjust the spark so that it occurs at the TDC mark on the pulley.

With engine running, spark should occur before the TDC mark on the pulley.

If the spark occurs well before the TDC mark with the engine running, the Wico mags' lag angle can be adjusted.

I have a book on repairing magnetos. If needed I can locate the book and let you know how to adjust the lag angle.
I have an excuse. CRS.

MikeEyre74
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Re: Wico XH mag timing adjustment...

Postby MikeEyre74 » Tue Apr 16, 2019 10:01 am

That’s going to be tough for me, since the starter is off and the generator is off and I don’t have a 6V battery. I only start the motor with the Handcrank. I’m not sure I really have any intentions of putting the starting system or the electrical system back together? It starts really nice on the crank, and it’s just a toy for me to enjoy in the yard, so I’m never going to be driving after dark needing lights or anything like that. I’m not sure if it’s firing at before or after top dead center come to think of it, I have to go home and look at it as I turned the engine over to see… Would that be of any use to you to figure out anything regarding my question?

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Rick Spivey
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Re: Wico XH mag timing adjustment...

Postby Rick Spivey » Tue Apr 16, 2019 6:44 pm

It should be sparking before TDC when running. The normal J4 mag retards the timing 13 degrees at starting, partly so there is no kickback to the hand starter. It is dangerous to hand start an engine with much spark advance, as it can kick back and hurt your hand or wrist. If your cub starts and runs well on the hand crank, I'd probably leave well enough alone.
Rick Spivey
'52 Cub ("Great Personality") 148xxx
'48 Cub with FH ("Gunny Cub") 38xxx
'57 Lambretta (a slow work in progress)
'74 Triumph TR6 (Mama's toy)

MikeEyre74
Posts: 44
Joined: Wed Apr 03, 2019 5:44 am
Zip Code: 06063

Re: Wico XH mag timing adjustment...

Postby MikeEyre74 » Wed Apr 17, 2019 9:56 am

So, I got the front end off yesterday to get started on the crank seal and took this picture. I figured I’d use it to show you what I had going on for timing:

D7C4DA06-A642-4003-8760-63E3EA387C4E.jpeg


Assuming the red arrow points to the TDC mark on the pulley, the yellow arrow points to where the timing pointer is indicating when the timing light is running. I think I’m running a little retarded for timing, if I’ve got that right in my head. Second opinion?

Eugene
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Re: Wico XH mag timing adjustment...

Postby Eugene » Wed Apr 17, 2019 10:04 am

MikeEyre74 wrote:I think I’m running a little retarded for timing, if I’ve got that right in my head. Second opinion?
That's correct.

Engine running, the yellow arrow should be about the same distant to the right of the red arrow.
I have an excuse. CRS.


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