I am rebuilding a Wico mag for a D2. It was given to me in pieces. Everything apart. I have it back together and just wanted to ask about the spark rotor. I notice that two of the teeth on the rotor drive gear (gear on the inside of the mag that spins the rotor) are ground down some and I figure that I should line the rotor contact with these teeth when I slip it into the mag. Is this correct? I am getting a spark from the Mag when I spin it by hand, so figure the rotor is in correct. Just want to make sure. Thanks for any help.

The Contact on the rotor should line up with the terminal in the cap when the points open.

Thanks. I realize that. It's just that there are always timing marks. I figure that these two teeth on the gear having a taper must be the timing marks. I assume that I line the rotor contact up with these teeth when I slip the rotor into place. I was just curious if anyone was familiar with this model magneto and could verify the intent of those modified gear teeth. The rotor has a gear and it is driven by this small gear that has the two tapered teeth. I'll go ahead and slip the mag into place and see if the pony runs. This is the first magneto worked on that the rotor had a gear under it. The rotors on my other mags are keyed and all the gearing is internal. But those mags are Eisemann and I think a Bosch.

I don't know much about the Wico mag but it would seem timing would be the same. With the drive flange gear mark aligned with the pony drive gear mark you'd want the rotor firing #1 cyl of the pony (LH cylinder viewed from seat). If that corresponds to your suspected timing indicator...you got it.

Thanks Old Magnet. I guess I just have to do manual determination. I can't find any info on this particular magneto. All my old CAT manuals show different versions. None of the parts books have a drawing of this version magneto. The D2 is in the 10,000 range, so it's a newer style mag. At first I didn't even think the rotor was for this mag, then I found this bracket part laying in the box of stuff the seller gave me and this bracket attached inside and had a shaft you slip the rotor over. When you slip the rotor in place onto this bracket, it meshes with the small drive gear. The drive gear slips onto the shaft that has the cam that opens and closes the points. I'll just do as everyone has suggested and slip the mag into the pony and visually determine if the timing is correct. I just like bench testing whenever possible. I'll take some pictures once I find the correct timing position.
Thanks for everyone's input.
And Happy New Year.

I looked through my stuff but all the Wico info I have is for units with impulse couplings and not the same configuration. Couple of pictures just for the heck of it:

Thanks. Yes, that is similar. The rotor is driven the same way. But the rotor is the older type that has the brushes that rub on the top of it as it spins. So, inside the cap it has those two brushes on springs that press down on the rotor. But I would expect that you'd have to insert the rotor in your picture so that the gears meshed in the correct timing position. Does your manual talk about any special attention paid to installing the rotor?

Oh, so on my mag, that small drive gear, there are two teeth that are tapered. And that gear is keyed, so it only fits one way. It must be that the tapered teeth have something to do with timing.

No, not getting anywhere with that info. The units I have material on are either direct drive or if gear driven the rotor is attached to the gear with a machine screw out on some radius so that it can't be altered. Instructions are heavy on going by the timing method that I earlier described. They don't say anything about a specific indexing of the rotor to the shaft.

What is the Wico number for the Mag you have?

Hi there.....I had these pictures of my Mag on my D2. Not sure if it will help but all I did was turn the flywheel on the pup motor so the indexing mark was facing straight up. When it was in this position I took the pictures. Not the greatest of pics but I managed to get things back together and running.

Green Horn, thanks for the pics. That isn't the same magneto as mine though. I've seen the type you have. Your rotor doesn't have a gear on the rotor, correct? The magneto in my question has a rotor with a gear on it and the rotor meshes with another small drive gear. The small drive gear has two teeth with a taper, which I assume is a timing mark. My question is when you slip the rotor in place, does the contact on the rotor point towards those timing teeth on the drive gear. I figure it does, but was looking for documentation on it.

I finally remembered to write down the Caterpillar part number.
p/n- 4S6471. I'll take some pictures of this mystery mag.