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BrianC 
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Joined: 16 Jun 2011
Location: New York
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 Topic: Magneto Timing Questions.
Posted: 15 Aug 2011 at 9:04am |
I am putting a new Wico magneto in a 1948 Allis Chalmers model C. I am confused with the timing mark on the fly wheel. I can see a stamped "F" on the flywheel from the inspection hole. F for "Fire"?. It appears to be somewhat before TDC. Is this "F" the high rpm running timing mark for after the impulse coupling drops out? At what RPM should this happen. Also, is this an "all-or-nothing" proposition, does the magneto operate in the starting lag mode and then normal mode only, or is there a progessive advance based upon RPM? I do not see a TDC mark. Isn't is essential when hand cranking that the the mageneto snaps at TDC or just after? I don't want it kicking back on me if I hand crank. How do you make sure it won't fire a tad too soon. The starter is running at 12 volts. With spark plugs out, the the engine spins fast enough I belive to make the impulse coupling drop out. With the cranking racket, hard to tell, but can that be? Would that happen with the plugs in, making compression? If so wouldn't that be bad-having it fire before TDC? This tractor last ran in the '80's. I want to get it going this week. Thanks, Brian
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Jeff Z. NY
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Posted: 15 Aug 2011 at 9:17am |
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If you turn the engine over and have someone wipe the flywheel with some WD-40 or something you may see the TDC mark show up.
Then I clean the flywheel and pain the mark white with a paint marker.
It should be 3 1/8 inches {30 degrees} away from he fire mark.
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wkpoor
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Posted: 15 Aug 2011 at 9:17am |
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There is a TDC but its marked "CENTER". With a Mag you need not be concerned with the "FIRE" mark. I wonder if Bs that originally had mags even had a FIRE mark on the flywheel or if that engine has been changed.
But in a nut shell install mag and rotate all the way towards engine, crank till you are on #1 Center, pull mag outboard till it snaps, lock down.
So look for the CENTER, it will be there. I doubt the 12V will crank enough rpms to override the impulse.
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Jeff Z. NY
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Posted: 15 Aug 2011 at 9:22am |
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Sorry that info was for a WD. WD's are only marked for Fire I believe.
On my C I found both marks by cleaning the flywheel with steel wool and then wiping the flywheeel with WD-40 while someone turned over the engine.
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Jeff Z. NY
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Posted: 15 Aug 2011 at 9:25am |
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Turning over the engine with the hand crank.
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wkpoor
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Posted: 15 Aug 2011 at 9:55am |
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I've seen the word "FIRE" on all my CAs. Makes sense ay engine that originally had a distributor option would have the FIRE Marked. Thats why I questions the B having it sense before a certain yr they were all Mags.
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wkpoor
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Posted: 15 Aug 2011 at 1:43pm |
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Well a friend of mine explained to me the all of the Bs have the FIRE mark because Allis's approach to mag timing was to first set engine on #1compression stroke with the FIRE mark lined up in the hole. Then install the mag with the rotor lined up with the #1 post. The impulse is compensated for when you do it this way. I personally prefer my method as you then know for sure where it will trip.
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Bill Long
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Posted: 15 Aug 2011 at 2:06pm |
If all else fails you may want to use the "finger in the number one cyl method". Frankly, even though we sold AC equipment from the middle 30's to 1962 we never used timing marks on the flywheel. In fact, we did not know they existed till I joined this forum. In any event remove the plug from the number one plug. With the finger in the spark plug hole turn till you feel the top dead center of the stroke. Remember, you are working with a non-sophisticated engine - and there is plenty of room for slop. When you get the engine started you can further adjust the timing by moving the mag on the ears. Remember, you can check the marks once you get the location with the "finger in the number one cyl method"
Hope this is some help. There are some web sites that explian timing much better. I am away from home but perhaps someone can chime in on the addresses.
Good Luck!
Bill Long
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TomMN
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Posted: 15 Aug 2011 at 2:43pm |
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Like Bill said use the finger in the number one cylinder method. Finding the timing mark will not tell you if you are at the top of the exhaust stroke or compression stroke. For this you need to use the hand crank; the starter will spin to fast you can't know where it is when it stops. Take the number one spark plug out and turn the hand crank until you feel air being pushed out around your finger then look at the set screw on the front crankshaft pulley, on a C it will be pointing straight up at TDC. The mag mounting slot should now be horizontal. Turn the mag backwards until the rotor points just a bit beyond the number one lug; its mounting will also be horizontal, then mount it to the tractor. The reason the rotor needs to be after the number one lug is TDC is 30 degrees after it would have fired while running. Once it is mounted you can verify when it sparks on number one easily by connecting the wire and plug to the number one spot on the mag and redo the finger in the hole until you feel air coming out then slowly turn with the hand crank and the impulse should make the spark right when the set screw points straight up; or the CENTER mark on the flywheel is visible in the timing hole.
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BrianC
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Posted: 16 Aug 2011 at 7:57am |
I got it started, it is running for first time in over 22 years. I never found a TDC or Center marking. I am confident the flywheel is original. 1948 model C. So the thumb method to find cylinder #1 compression stroke, install mag, next snap of mag , that post was designated #1. A little ether to help, and it started. I painted a white line at the stamped F marking. Put a timing light on it, but it did not show up. I tried all 4 spark plug wires. The strobe works, but no white line in the inspection hole. I rotated the mag some untill it sounded best, still no F mark with strobe. This surprised me. F mark, what is it good for. I wonder when the strobe light was invented, and in common use. It sounds pretty good, that old sound I remember. Purrs , idles down low. The fan is blowing chunks of rust and dirt, they sting! So I met my goal, start it up and drive it around. Now I am looking at all the other work. What is it about springs? Clutch, brakes, starter rod return springs all returned back to earth dust. Thanks for your help.
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TomMN
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Posted: 16 Aug 2011 at 10:47am |
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Great to hear you got it going. Maybe someone can tell us if the flywheel can only be mounted one way or if it could be mounted so the F mark will not be in the right spot. But like Bill said; many didn't even know the timing marks existed and always made them work.
Yes, the springs exposed to the elements all these years are many times gone or a half is hanging useless in the breeze.
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wkpoor
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Posted: 16 Aug 2011 at 11:31am |
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Was it stored outside with tall weeds all around it or under trees. Nothing wrong with outside, got plenty of my own stuff outside, but away from vegetation. Under trees or surrounded by weeds and they go away fast.
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CTuckerNWIL
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Posted: 16 Aug 2011 at 12:08pm |
 TomMN wrote:
Great to hear you got it going. Maybe someone can tell us if the flywheel can only be mounted one way or if it could be mounted so the F mark will not be in the right spot. But like Bill said; many didn't even know the timing marks existed and always made them work.
Yes, the springs exposed to the elements all these years are many times gone or a half is hanging useless in the breeze.
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If I'm not mistaken, all flywheels have one odd hole. They only way to mount them wrong would be to only use 2 of the bolts to hold it on.
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Dick L
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Posted: 16 Aug 2011 at 12:52pm |
On not seeing the fire line with the timing light. You are one tooth off inside the magneto. With the magneto tipped as far as it will go to where it sounds like it is running good the line is just out of sight. The engine will sound good but under load you will feel like it is low on power. I have gone thru that very thing more than once when checking points without removing the magneto. After having it slip on me a few times I now remove the cap and tape the rotor fast before removing the points cover. The timing light hooks to number one plug wire always. When in time I have never had the magneto tipped all the way one way or the other. Always seem to be tipped slightly toward the engine when the fire line is in the center of the inspection hole.
I am talking about an FMJ magneto above but the Wico should work close to the same.
Edited by Dick L - 16 Aug 2011 at 12:59pm
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