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Farmall Cub • View topic - magneto oil seal

magneto oil seal

Thu Dec 19, 2013 2:04 pm

I have a 52 cub and when I went to change the points the mag ( J4) was half full of oil. I decided to change out the seal. Now I cannot find one, the number is CR 251379-something 91 Can anyone help me out?

Re: magneto oil seal

Thu Dec 19, 2013 2:36 pm

Welcome to the forum! Go to your local parts house and tell them you need a National 450313 seal.

Re: magneto oil seal

Thu Dec 19, 2013 3:10 pm

Barnyard wrote:Welcome to the forum! Go to your local parts house and tell them you need a National 450313 seal.


Or an SKF 20747, same as the National 450313. They're under $10 at Advanced Auto Parts.

Re: magneto oil seal

Thu Dec 19, 2013 4:32 pm

Thanks for the info. Much appreciated

Re: magneto oil seal

Thu Dec 19, 2013 8:31 pm

Only seat the seal 23/32 deep. There is no lip to keep it from sliding for enough in to rub on the gears.

Re: magneto oil seal

Thu Dec 19, 2013 11:52 pm

I had made this from an old worn-out carrier.

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I ground and filed off the oil slinger on the one side of the carrier so it would not damage or interfere with the seal while driving it in.

Image

One bolt a nut and a couple of flat washers and you have a great tool. The lip on the carrier will stop and set the seal at the correct depth. When I put the nut on I used the permanent Lock-tite.

Image

Re: magneto oil seal

Fri Dec 20, 2013 9:55 am

Criswell wrote:I had made this from an old worn-out carrier.

Image

I ground and filed off the oil slinger on the one side of the carrier so it would not damage or interfere with the seal while driving it in.

Image

One bolt a nut and a couple of flat washers and you have a great tool. The lip on the carrier will stop and set the seal at the correct depth. When I put the nut on I used the permanent Lock-tite.

Image


Nice fabrication! Can that be used with the governor in place or removed?

Re: magneto oil seal

Fri Dec 20, 2013 10:37 am

I'm going to jump in on this thread and ask a question. On my Cub, Merlin, the mag oil seal was leaking when I got it. I replaced the seal and drove it in to the prescribed depth. Guess what... still leaked! I tried tapping it in slightly deeper to see if I could get past any ring that was on the governor. Still leaked. Thought that the seal might have been defective, so I got another one and lubed up the governor for installation. I tried it at the correct depth, and STILL got a leak. I have looked at the housing as well as the shaft of the governor, and they all appear clean and smooth. I do not have the gasket between my mag and the governor housing, and I am glad for that since the oil can then find a path out of the tractor instead of into the magneto. Any ideas? Replace governor? Change installation technique? I'd really like to stop this leak as it attracts grass when I am mowing!

Thanks all!

Mike

Re: magneto oil seal

Fri Dec 20, 2013 11:13 am

Mike,
That is a good question. I have researched the posts on that subject and found there are magneto oil seals that have different widths, and as a result some of those have to be driven in about 1/8" further to get a good seal. I believe that is the reason that Earl made his tool with a separate lip to account for the different widths when driving the seal in place. The problem is that I cannot find a definitive explanation that tells what width seal must be driven in 23/32" (as noted in the manual) and what width seal must be driven in a little further. The seal that I just purchased from the IH dealer is part number 251379R91. It is manufactured by National and is their part number 450313. it is 0.5175" thick.

Hopefully, someone can shed some light on this issue.

Re: magneto oil seal

Fri Dec 20, 2013 11:45 am

I replaced my seal 2 years ago and it just started leaking recently. I wonder what's up with that. I would think it would leak right away or work longer than 2 years, and it doesn't have that many hours on it.

Re: magneto oil seal

Fri Dec 20, 2013 2:07 pm

Bill E Bob wrote:Nice fabrication! Can that be used with the governor in place or removed?


Thank you. The one that is shown in the photo works when the governor has been removed, but not while the governor is installed. I also made one that can be used while the governor is still installed. Instead of just taking off the oil slinger I took off the entire boss so it was completly flush on the one side (you can do this with either a lathe, mill or a good hand file, this last one just takes longer). And fear-not, these were not made from good or serviceable parts, both were completly worn-out. There was/is plenty of clearance to use the other one that I had made while the governor is still installed, I just don't have a photo of that one handy.

Re: magneto oil seal

Sat Dec 28, 2013 4:30 pm

Thanks for all the info on the oil seal and installing.This was not the most easy seal to locate,got two on ebay for $10.00. Installed seal to required depth,installed magneto and it fired right up, air temp 24 degrees. I have had this Cub for 20 yrs. and it plows snow all winter, the only problem is that it is hard on spark plugs. I usually get one season to a set of plugs. My driveway is 1/2 a mile long with 1 part up to 10% grade for 300 ft.very little flat ground. I have tried all brands of plugs,all of a sudden it will start to missfire,change the plugs out and it's good for another season, any ideas? Thanks everyone and have a great New Year

Re: magneto oil seal

Sat Dec 28, 2013 6:05 pm

Don't know about your situation, but I had Honda motorcycle, and if it started missing might as well change the plugs. Also had a VW pickup (Rabbit) that would burn the gap beyond the limits of my gauge in about 5K miles. Eventually had to change out fuse panel. When the alternator and battery had to be replaced the problems went away (went to larger alternator. 65 amps)

Re: magneto oil seal

Sat Dec 28, 2013 6:27 pm

My 53 Cub is the same way with spark plugs. I don't work it anymore and start it occasionally to keep the battery up, and they load up with carbon. I started running it at high rpm and it doesn't miss a beat, but it will need plugs in about a year.

Re: magneto oil seal

Sat Dec 28, 2013 8:04 pm

Thanks Tom.When the cub runs it is at full throttle due to the grade it has to pull,in 2nd gear it pulls great,but the plugs are carboned up,electrodes are white.Maybe time for a carb rebuild or new coil in mag.Any ideas out there??