Magneto Timing Position

[billpedalino]

Murph,

Yes, I am using the 3 insulators between the Linkert and the manifold. However, I went through all of my old magnetos and panhead/knucklehead timers (they have the same drive gear) and noted that the hole locations are slightly different on some gears. It appears that the hole locations are not really indexed acurately when drilled. I'm going to remove one of the gears that has the hole located approximately 1/2 tooth out from the gear that I'm using and see if that work any better.

[murph]

You are using the 3 factory spacers between the carb & manifold for the xlch correct? I had the similar issue as you can see it is very close but works. You can just about fit a piece of paper between the mag and air cleaner.

[Sargehere]

Location of the hole in the gear makes not a whit of difference. The gear teeth are symmetrical all the way around. I've used Fairbanks-Morse Sportster magnetos in my ULs many times, and never had a problem pulling the mag up from engagement with one cam tooth and dropping it down to engage another; it's just a matter of finding a position for "advanced" that you can live with that will also allow you to turn it to "retarded" position and back. I doubt that there's any reason to disassemble your entire cam chest. I've never found one that you can't adjust.

It's a combination of finding where the engage the gear on the cam so that the narrower end of the points cam is about to break the points, and that the mag is allowed to retard (clockwise) from that point and where the mag body points when that happens. There should be at least two positions, using the stock Sportster parts. May I suggest that you don't think "one tooth" this way or "one tooth" that way, but more like "pull the sucker out and spin it around!" (?)

[billpedalino]

Gentlemen,

I'm installing the magneto into my Sportster motor and there is a problem with the magneto position when it’s properly timed. This is a 1964 CH which uses the DC Linkert with the round air cleaner and lever-choke. When the motor is in the front cylinder firing position (Front intake valve returned-down and timing mark in center of hole) and the magneto body turned counter-clockwise until the points just start to open, the magneto is turned too far out and it interferes with the air cleaner backing plate. Advancing the rotor drive gear 1 tooth on the cam drive (36° of rotor rotation) advances it way too much and the magneto is too close to the rear cylinder. With the magneto that close to the cylinder, I can’t get any spark retard for starting. Also, I’m using the ’65 and later advance setup (I also have the original 'locked-magneto' plate' as well). Yes, I know it’s wrong for 1964 and that the judges will 'correct' me by assigning the appropriate point deduction, but preserving my 62 year old bad knee that was damaged in starting this very bike at age 20 is certainly far more important than a couple of AMCA points, should I choose to have it judged.

People familiar with Sportster magneto setups will probably inquire as to the following:

1. I checked the motor timing position twice and its correct.
2. I checked the point gap and its correct (as I suspected as you installed them).
3. I tried one tooth back and one tooth forward on the magneto/cam gear purchase.
4. I used the old pin temporarily to mount the gear, as I suspected that the gear might have to be removed, turned and replaced.
5. The tapered screws for the cam cover-magneto mounting plate to not protrude above the flat magneto mounting surface.
6. The magneto sits flat and squarely, and bottoms onto the mounting plate.

In the past, I’ve had this trouble with aftermarket gears that had an incorrect hole location. But this is an OEM gear and rotor. In fact, I compared this gear to another OEM gear from another original magneto that I own and the pin hole looks to be identically located, so I suspect this is not the problem. Also, it appears that turning the gear 180° on the rotor shaft will not help, as there are an even number of teeth and flipping the gear yields the same magneto firing position. I’ve attached a photo of the two OEM gears placed together. As you will note, the holes are drilled in identical locations.

I’m now thinking cam gear timing, as I just can’t think of any other reason why the magneto is out of position. It’s all OEM parts and it was certainly positioned properly when it left the factory. Having built many, many Sportster motors I always pay careful attention to breather, pinion and cam timing during assembly - but maybe I screwed up? But at this point I know that I’m second-guessing myself, as I installed the cams over a year ago. If I skipped a tooth on the cam, I would think that it might throw the magneto position out as indicated, but I’ve never made that particular mistake so I don’t know for sure. Also, I'm not sure tha the drive (worm) gear on the end of the cam would advance the rotor gear enough to cause a substantial swing in the mangeto body if I'm only one tooth off - but possibly.

I know I'm being lazy, but God how I hate to remove the cam cover and disturb a now-pristine, newly assembled cam case. Therefore, with the advantage of maturity (nicer way of stating 'old') and experience, I'm reaching out before I disassemble. If anyone can offer any other credible suggestions before I remove the cam cover, I would greatly appreciate it. I've seen this problem before, so I'm certain that some of my fellow motor builders out there in the 'cloud' have dealt with this as well.

Thanks ...