Farm Equipment - C model mag problems

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C model mag problems

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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=32999
Printed Date: 10 Jun 2024 at 9:53am
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Topic: C model mag problems

Posted By: Don(MI)
Subject: C model mag problems
Date Posted: 28 Jun 2011 at 7:47am

Well, my ol gal decided to quit running last night.

Here are her symptoms.....Lots of gas, clean carb (zenith). Weak spark off the mag points. This is a 12 v. system.

My questions.... Whats the best way to make sure I get the TDC mag timing correct?

Also, with these mags, whats generally the first thing that goes bad in them?

(I know this has been on here many, many times, but my failure to pay attention finally caught up to me! Usually, the only way I learn, is if I am dealing with the same problem and have to fix it myself!) This lead to the other thread about having a sub forum for FAQs, I think we need it!

Thanks, Don

Replies:

Posted By: Jeff Z. NY
Date Posted: 28 Jun 2011 at 7:53am

First thing to do is to set the points correct and try it.

Posted By: Steve in NJ
Date Posted: 28 Jun 2011 at 8:00am

Clean the contacts off first with a tuner cleaner or Brakekleen, then re-set them. While yer' in there, toss a new condenser in. Those little buggers make folks pull their hair out. There really isn't a "first" thing that goes in a Mag. Any failure in a Mag can cause a problem large or small. If you wanted to be technical about the first thing to go, I would say the Magnetic field in my own personal opinion.....

mailto:Steve@B&B - Steve@B&B

Posted By: Chuck(ONT)
Date Posted: 28 Jun 2011 at 8:04am

Make sure plug wires are solid copper, and not resistor type, also plugs. 12V makes no difference, mag is generating its own spark(when operating). re mag, points, condenser and coil. The older coils when heated can short out, then be ok when cold.

-------------
Never take life too seriously.

Nobody gets out alive anyway!

1C 1 WD45 1 AC180

Posted By: Don(MI)
Date Posted: 28 Jun 2011 at 8:05am

Thanks! I wondered about the condenser.

Posted By: Jeff Z. NY
Date Posted: 28 Jun 2011 at 8:22am

Right Steve, So many people rebuild a mag and don't have it remagnetized.

Posted By: Jeff Z. NY
Date Posted: 28 Jun 2011 at 8:26am

I was running the B and it ran OK.
The next time I went to use it sounded bad.
Weak spark, skipping, backfiring.
Points were not opening correctly.
Reset the points and away we go.

Posted By: Dick L
Date Posted: 28 Jun 2011 at 8:30am

I just spent over two hours last Saturday on a magneto. I changed points and condenser several times as well as trying three different magneto bases. Could not get spark at the points in a vise. I have the points that were new from a magneto that have lost the magnetic pull. I had other points that looked like new that came from used magnetos. I finally broke down and opened a sealed set of points and I had spark. After I installed them of course. Placing the magneto back on the tractor in time has become a problem with my crippled up hands and elbows. I found a new way for old crippled up old men, girls and boys. In the vice I checked the spark with the magneto re assembled with wires. After checking each terminal several times I stopped after I had spark on the number four terminal. I then placed a strip of masking tape over the impulse drive so it could not turn backwards and be ready to fire number four terminal instead of number one being next. This is the way I have always done this though. Trying to crank and check for air from number one plug hole and finding things didn't bend sharp enough to feel the air until I was past the point I could get the drive to match the lugs several times I then placed my thumb over plug hole number three. (the last to fire before number one) After feeling air pressure I then watched the drive as I turned the crank to see it past the firing point for number three and then kept turning the crank until the lugs would enter the drive. That put me in time. If you are in time before removing the magneto a little pencil mark on the magneto and where if mounts will make sure it is in proper running time.

Posted By: wkpoor
Date Posted: 28 Jun 2011 at 8:50am

I just put one on Saturday and this is my explanation.
First put engine on #1 TDC The word "center" will appear in flywheel window. Disregard the word fire that will appear before you reach center.
Install mag with rotor pointing towards #1 tower ( might need to remove rotor cap to see where that is) and rotate fully towards engine inboard
Install mag and just snug bolts a little.
Ground mag with sw or jumper wire.
Rotate engine 1 3/4 revolutions or 3 snaps of the impulse.
Now carefully rotate till the word center is centered in the window...stop!
Rotate mag outboard till it snaps.
Lock it down and you done! Timing is preset in the mag.

Posted By: Don(MI)
Date Posted: 28 Jun 2011 at 9:20am

Wow, thanks!!

One more question.... The main shaft in the mag, with the gear on it that drives the points. Should this shaft be slipping? We noticed last night, that every 3/4 of a turn, it slips and does not rotate with the crankshaft when we roll the engine over by handcrank.

Posted By: Gerald J.
Date Posted: 28 Jun 2011 at 10:20am

That "slipping" is the impulse starter winding up its spring. It spins the shaft fast enough to generate good only while cranking, makes for way better starting than without it.

Gerald J.

Posted By: wkpoor
Date Posted: 28 Jun 2011 at 12:35pm

Without the impulse you typically would not have enough rotor speed during cranking to create primary winding current flow.