[Farmall] Another O-12 project, part 8

[Karl Olmstead]

Spent a lot of time this past weekend on other projects.  Used my Kubota backhoe to dig up a leaky water line on a property I'm developing.  Found that the 1.25" line had pulled apart at a glued joint.  Don't know the cause; bad glue, improper installation, or just bad luck.  Leaky water lines aren't difficult to locate in the Mojave desert; just look for the lush growth of weeds.

In keeping with my plan to process x-12 tractor parts in batches, I disassembled ten F4 magnetos.  I have about 50 of them, some taken from F-12s I've acquired, many purchased at the Tulare, CA swapmeet; more bought from ebay auctions.  I discovered that if an ebay seller has one F4, he or she probably has two or three more that he/she would be happy to sell as one bunch.

Back when I first started rebuilding magnetos, I selected the worst ones in my  collection, in particular the ones without distributor caps.  Sitting open to the weather is really hard on magnetos.  By restoring the worst ones first, I reduced the risk of damaging a good magneto while I was learning to work on them.  And the tricks I learned then make working on better magnetos a 'piece of cake'.

Arbitrarily selected eight F4s with the 'conventional' impulse, and two with the E4A automatic impulse.  The two types are incompatible; those with E4A automatic impulse are about half an inch longer than normal F4s.  That early O-12 I bought last fall really should have a magneto with the E4A impulse on it.  The fact that it doesn't tells me that somebody has changed the magneto mounting bracket.  My '31 T-20 uses the early F4 also.  It came to me with a Fairbanks-Morse magneto, but I replaced it with a rebuilt F4.

I haven't done much magneto work for three or four years, and the first one I dismantled had the E4A impulse, so it took me an hour or more to get it torn down. 
After that, I remembered the process, and the rest took half an hour or less apiece.  Except for one.  As soon as I examined it, I expected problems.  It was caked with mud.  It had obviously spent time in the dirt, probably in a mud puddle.  I tried scraping mud off the screw heads with a screwdriver, but that took too long.  So I carried the muddy mag over to my sandblast cabinet and blasted the mud and grease off the screw heads.  With the screw heads exposed and slots clean, all but one of the screws came out, although it took a LOT of force.  Half of one screw head snapped off.  I've found two ways to cope with this.  You can knock off the other half of the screw head using a hammer and chisel, or try grabbing the screw head with a pliers and unscrewing it.  In this case, the pliers worked fine.

The magneto drive disk, which is a free-floating disk that couples the dogs on the magneto impulse to the dogs on the engine magneto drive, was stuck hard to the impulse.  I sandblasted it, oiled it, and pried it off.  The impulse parts that hold the impulse spring were rusted together, so I pried them apart and tried to remove the spring.  It broke as I pulled it out; rusted almost through.

Cleaned up the points cup and oiled it well; put the points cover back on and beat on the lever with a dead-blow hammer.  The cup freed up and I got it out.  The magneto rotor was stuck to the case.  Sandblasted the crud out, then pressed the rotor out using a hydraulic press.

Net result was a good case, good distributor disk and magneto housing, but worthless rotor, gear, bearings and points.  Still a fun project!  This just happened to be F4 magneto number 140,000, so I wanted to salvage it just for its unusual serial number.

Tonight I sorted out the bucket of parts I had accumulated.  Magneto coils in one plastic bowl, distributor rotor assemblies in a coffee can, impulse parts in another coffee can, electrical parts in a plastic bowl, all bearings and related parts in another bowl.  Decided to test the coils before wasting any time cleaning them up.  to my surprise, eight out of ten coils were good, based on resistance measurements.  The primary winding resistance should be from 0.2 to 0.4 Ohms; the secondary around 12,500 Ohms.  Removed the soft iron core from the two bad coils, then threw the coils away.  New coils don't include cores, so you need to keep the old ones.  Past experience has shown that about half the coils are bad, so 80% good on this batch was good news.  I'll bet coils cost $75 or more nowdays.

I've been using diesel fuel in an ultrasonic cleaner to clean up parts.  It doesn't work very well.  Hope NAPA still sells those hydroseal carburetor cleaning baths.  Expensive, but very effective.  I'm thinking that diesel fuel in the ultrasonic bath may do good things to the rusted up impulse parts.  Can't hurt to try.

Anyway, the net result is that I am still accumulating parts to clean and paint.  Still need to do a bunch of carburetors.  Once I get enough parts primed, I'll start topcoat painting.  I don't have much hope that I'll have this particular O-12 running for the Tulare antique tractor show, only one month away.  I could have done it if I was willing to fix up just one magneto, carburetor and fuel pump for that tractor, but once I decided to do a whole bunch of each component, I started falling behind schedule.

I think that I've figured out how to fix up the rusty round spoke front wheels.  I needle scaled one of them a week or two ago, but the original rubber covering the inner end of the spokes was a problem.  I think I can rip it off with a big hand-held angle grinder equipped with a wire wheel.  


-Karl

_________________________________________________________________
Windows Live™ Groups: Create an online spot for your favorite groups to meet.
http://windowslive.com/online/groups?ocid=TXT_TAGLM_WL_groups_032009