Hi All,

   Can anyone offer me a brief description of what the seal between the timing chest and magneto shaft looks like? The bore in my cases where the magneto shaft passes through into the timing chest has had some obvious repairs and been re-machined. It looks a a bit rough and I'm trying to determine if it is fit for purpose or needs more work. The back of the magneto gear looks to me like it might be an oil slinger but I'm unsure of what provides the seal between the magneto and the timing chest (around the shaft).

I'm about to dowel the cases as the original spigots are way too sloppy and I want to get all welding work out of the way before beginning the dowel and main bearing machining. If the seal is a bit of felt or similar between the magneto and timing case housing I'm guessing the current state of the bore is fine. If something must be pressed into the housing bore it may need more work.

Hope that made some sort of sense to others.

Regards,

Ashley

Peter is right, a felt washer. I cut out of a 5mm thick felt sheet a washer at roughly the same size as the mag gear.

The slinger at the back of the mag gear function in conjuncture with a steel ring that is pressed in the cam chest. Air is pulsating slightly and oil mist can migrate to the outside. The gear ring do sling most mist outward by centripetal force, and then the cam chest ring together form a kind of "silent compartment" or labyrinth where fresh air is entering the cam chest. The little oil mist that remains is slowed down in the labyrinth to be collected in a groove, and evacuated via a small hole at the bottom.

That ring in the cam chest can sometimes be worn out or discarded with but that seems not be of that great importance. What is more important is the felt washer that prevents water spray and dust from the front wheel to enter the motor.

The motor needs fresh air for the ventilation to function properly and perhaps even for the lubrication to work properly, so it's not that great idea to make an air tight seal there. In a pinch the washer can be cut apart in order to be mounted after the magneto is fastened. Or a couple of turns with thick soft cotton yarn can be used, it is better than leave it open.

In the case of the later motors where the ventilation is moved to the cam cover opposite the mag gear, the labyrinth may be of greater importance as the direction of the flow of air is changed. From what I can read in the parts list, they both have the same felt washer 26 B 105 Magneto shaft cam case felt washer.