F-4 magneto

[farmalldan4]

Does anybody know of a good source for a rebuilt F-4 magneto for my F-12? I do have a core.

Thanks
Dan

 

[rustred]

what is wrong with yours?

 

[farmalldan4]

I have 2 of them. One, I can't get the impulse to work properly. The impulse does engage. I have squirted penetrating oil into all of the oilers. It just seems sluggish like the impulse is working, but the bearings are tight and doesn't get the quick snap that it needs. Don't know if that one is producing spark or not. The other one doesn't have spark.

 

[rustred]

very simple fixes. take the impluse apart and clean the dryed up old grease and lightly oil it. as for spark check the point. clean and gap them. sometime they need a condenser not very often tough. dont be putting a lot of oil in them oil caps. do more harm than good it tell you right on them.one thing about a magneto , they are very dependable unit.

 

[teddy52food]

I have a good one on the shelf, but could make yours work too.

 

[Dave41A]

The manual used to be available over at the cub forum. The same manual covers the F and H magnetos. I used it to rebuild two of the H4's a few years back--following the book really tuned them up! It is an excellent reference. The F is different design but the principle is the same. If they are complete, I think you can get them throwing hot sparks again with not too much work.

 

[wore out]

(quoted from post at 12:36:47 04/20/21) The manual used to be available over at the cub forum. The same manual covers the F and H magnetos. I used it to rebuild two of the H4's a few years back--following the book really tuned them up! It is an excellent reference. The F is different design but the principle is the same. If they are complete, I think you can get them throwing hot sparks again with not too much work.

http://farmallcub.com/rudi_cub/www....s/GSS-5035 Service Manual Magnetos/index.html

 

[farmalldan4]

Thanks to everybody that replied. I finally have spark on both of them. Just needed some brake cleaner on the bearings of the one that was sluggish. The other one still has a problem though, sometimes when I turn it through the impulse it goes past the next stop; example: if I am on number one cylinder and the impulse trips I get spark then I go to number three cylinder and it has no spark. When I pull the cap off, the rotor is past number 4 and is ready to fire number 2. The other mag should work OK, so will put it on and try it.

Once again, thanks for the help guys.

Dan

Grass is green, Tractors is red.

 

[rustred]

yep, so if they are not red leave them in the shed!

 

[Dave41A]

(quoted from post at 21:52:43 04/20/21) The other one still has a problem though, sometimes when I turn it through the impulse it goes past the next stop; example: if I am on number one cylinder and the impulse trips I get spark then I go to number three cylinder and it has no spark. When I pull the cap off, the rotor is past number 4 and is ready to fire number 2.

The firing order should be 1-3-4-2. The impulse trips with quite a lot of released spring energy. I can see a magneto tripping the spring and spinning the "armature" nearly 360 degrees--in other words, right past 3 to 4. It would have sparked #3 on the way--just so fast you couldn't see it.

But you write that it is actually past 4 and ready to spark 2? This is confusing. That would mean the coiled up spring energy was spinning it past both 3 and 4, and putting it in position to fire 2. I guess it's possible, but that would mean the armature, upon impulse release, was spinning through a full 1.5 turns after release (the "rotor" is geared down from the armature 2:1). Recall the F4 flyweights disengage the impulse pawl at speeds as slow as 180 rpm and won't re-engage until the mag is down to as low as 125 rpm.

Honestly, I would try it on a tractor and see if it works. You probably just have a really stiff impulse spring that gives the armature a good spin. Either that, or your flyweight bearings may be a little sticky, meaning the flyweights don't fly back out and re-engage the pawl. This is shown on page 25 of the manual.

You could also install plug wires and plugs on the mag to watch for spark while you bench test it. I'll bet that plugs 3 and 4 are firing while the rotor is on its way to #2.

Good luck, Dave

 

[farmalldan4]

I put the sluggish mag on and it fires in order. Now I just need some fuel and try to make it go. I haven't ran this tractor for probably 15 years and it has just been setting outside in the elements. When I parked it it was using more oil than gas. In the meantime, the wife thought it would be a good idea to move to town so I parked the tractor at a neighbors and left it. Last fall I thought it would be a good idea to have it hauled in to a storage unit since I don't have a shop anymore. I put liners, pistons rings and bearings in it so it should do a lot better.

Dan

Grass is green, Tractors is red.

 

[Dave41A]

Sounds good. Please post pictures or video of the old iron coming back to life!

 

[Ken Christopherson]

I would give Rudy Calin a call. He is one of the nations best! I work for him on occasion to help him out when he is busy, and he has a ton of F4 mags. Will take yours in as a core as well if you have one. Search for rebuiltmags on the old Google machine and you will find him easily.

 

[farmalldan4]

I talked to Rudy and he said he was on his way to a show and that all of the F-4 mags he had were spoken for and to call him back on Monday. I think I have the problem solved but if not, I will be in contact with him.

Dan