Magneto seal

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Magneto seal

Postby aei707 » Mon Feb 04, 2019 9:03 am

I had to remove my magneto and found out the seal between the mag and the governor was leaking and needed to be replaced. Since my mag is out and my governor needs to also come out. What is the best direction to replace the seal and where does the seal land between the two

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Re: Magneto seal

Postby wrz » Mon Feb 04, 2019 11:11 am

You don't have to remove the governor to replace the seal. Take an awl and punch two small holes 180 degrees apart on the metal ring of the seal. Next step is to use two sheet metal screws the right length so that after you screw them in the punched holes you can use a cats paw to pry on each screw head to pull the seal out.(back and forth) The hard part now is when you install the seal it only goes in so far. I use a gauge that farmertan made to set the seal the right depth.The service manual shows the correct depth. Another trick is to take electrical tape and wrap a layer around the the hub so when the seal slides over the slots for the mag drive it won't nick the rubber seal. Remove the tape after the seal is in place. The awl works better than a drill because you don't have to worry about the chips getting in the engine oil.

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Re: Magneto seal

Postby Ahab01 » Mon Feb 04, 2019 12:10 pm

The manual says it goes in 23/32" from the ignition mounting surface. Just make sure it goes in square to the surface and check the shaft for wear where the seal contacts it.
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Re: Magneto seal

Postby inairam » Mon Feb 04, 2019 3:14 pm

The seal goes in from the mag side. If you have a lath or access to a friend with a lath there is a tool you can make. do a search for "governor seal tool".

Before you set to the 23/32 measure the current seal and the replacement seal. If there are different ( the new one is probably thinner) do the math and change the depth. The oil being sealed is coming from the governor side. I felt the position of the back of the seal was more important than the front.

Before you reassemble, put the engine at TDC #1. I would also pick up a paint pen or chalk or punch something so you can mark the gears. Once the seal is in place you can not see the timing marks. If you are off gear with the mag it is very difficult if not impossible to time the mag. read about installing the mag and timing the mag before you reassemble.
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Re: Magneto seal

Postby Glen » Mon Feb 04, 2019 6:40 pm

After removing the old seal, you should clean the surface on the governor gear where the seal runs, the whole length where the seal rubber will be sliding over, so the new seal rubber is not damaged sliding over rust, or rough metal.
Use fine sandpaper on the surface, if it is rough, and smooth it.

If the governor gear seal surface has a groove worn in it where the old seal was running, it's better to install the new seal so the rubber will run on an unworn part of the surface.
Like was said above, the new oil seals are probably thinner than the old seals shown in the manual, so it might need to be put in to a different depth than the manual shows.

Oil the surface before installing the new seal, and be sure the seal lip stays facing ahead, and straight as you drive the seal in over the gear surface.
Don't hammer directly on a new seal, put something metal or wood over it to hammer on. In that position, with the governor gear there, some of the people on here have made round tools, with a hollowed end, to fit into the hole, and over the governor gear. :)

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Re: Magneto seal

Postby Posco » Thu Feb 07, 2019 7:52 pm

Someone here used to make a device for seating mag seals. I bought one from him and still have it.

Before I got my hands on that I used 23/32 plywood as a depth gauge. I cut a round piece of 23/32 just slightly smaller than the seal itself. Used a flat piece of hardwood to get the seal started and then placed the 23/32 plywood piece over the seal and drove it home with a mallet. The hardwood board over the plywood prohibits you from driving the seal deeper than it is supposed to be set. They are not easy to get seated. The worst experience of my Cub life was getting that governor back in its proper place

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