fairbanks magneto

ok heres my problem i have rebuilt the motor on a a/c model c and the mag wouldnt fire so i took it apart to clean the points up the book shows me how to time it with the marks on the gears the small gear has one tooth filed off on a 45% but the big gear has no marks on it the book says it should have two marks one that is CW and one CCW but with out these marks how do you time it some one did it before me so there has to be away. thanks every one for your help

I just did my new C last week and can tell you how I did it, which worked but may not be correct. I took out the plugs, put my thumb over the hole for #1 (closest to the radiator). I turned the crank till I felt compression and then shone a light and peered in till I saw the piston come up and stop at TDC, more or less. I then set the mag so that the rotor pointed to 10:30 and it fired right up. I may be off by a few degrees, but it runs and has power, so I am satisfied. Firing order is 1243 and the rotor turns clockwise as you look at it. I hope that helps, and if not someone more experienced will be able to tell you how to proceed.
Zach

i know how to do all that i am talking about inside the mag there are to gears that time the mag but thanks for trying any luck some one will know a trick how to do it

For years before I knew the prim and proper method I simply put the drive in a posistion whre the points just began to open and the rotor then needs to be pointed at a post. First off, make your life easy and take the thing clear off the tractor. An important thing to remember is the mag fires when the points open and this does not change when you lose the mesh of the gears, it is till firing it just isnt going to the right place, (or to nowhere depending on where the gear is meshed). The mag turns clockwise as you look at the drive lugs but you cant be fighting the impulse to get where you need to be so you have to turn it backward to when the points just close, then the other way until they just open, a test light helps here, you dont want the points wide open but just barely moving, just loosing contact. This happen twice in one turn, you want the drive lugs to be about straight across not up and down for easier timing later. OK, once you have the points just opening and the drive lugs about straight across you need to hold that position while you install the rotor gear so the tang on the rotor is pointed to #1 which is the top inside terminal. Remove the plugs and wires from the engine and use them to check your work (the need to come out anyway) by turning mag and tripping the impulse. I do this in a bench vise but dont clamp the mag too tight in a vise. The plugs of course need to be grounded to the vise also. crank the motor by hand until #1 is TDC compression stroke, The mag drive dogs in the block should be straight across. Remove the small cap from your mag and get the rotor pointed towards #1 again and check the dogs, should also be straight across. Install the mag to the middle of the slot and you should be good to start.

do as Zach said, with the mag on the tractor, get piston 1 to the top and then put the rotor at the timing mark and slip the cover on. put on the cap and wires. I did that to my B 2 years ago when I set the points. Bob

I think what your asking is to time the rotor in the cap? On the face of the composition gear there should be a small dot on the gear near the teeth. Turn the brass gear so the notched tooth is pointed up. Take the outer cap off the inner cap. Spin the rotor till it's approching number 1 position gently while holding the rotor still with your finger slide the cap on the mag holding it about 1/2" higher than mounting positon. Slide the cap down the face of the mag while stopping the rotor from turning. Screw in place, screw on outer cap. Worst case you might be off by one tooth, if so repeat procedure.

If you point the rotor to the 10 oclock position you will find that is the index for number one and will index with the matching gear.

This link of Rod's guide should help you. The fiber gear originally had a ink marks of C for CW and A for CCW that fade off or grease & oil take off after time.
FM J timing for AC

thanks every one maybe ill have it running saturday ill keep eveyone up dated