• Dana

Magnetos

I've been on the road for work a lot lately so I haven't made much progress on the bike lately. But, I did get a chance to rebuild one of my magnetos. I've learned a lot about magnets and ignition systems over the last few weeks. I didn't know magnets lose their magnetism over time, and they need to keep the magnetic flux intact otherwise they lose their strength. And, I've been working on cars now for years and only had a vague idea on how ignition systems actually worked. Like 'dwell' I've measured it for years, before I upgraded to electronic ignitions anyways, and only now just learned what it actually is. It's just the amount of time the points are closed. 'Condenser' that's just a high voltage capacitor.


The Splitdorf NS2 is a pretty simple device. Points, condenser, rotor, coil and a big magnet. That makes the high voltage. A distributor and cap send the high voltage to the spark plugs and you get a spark.


Anyways, I have three magnetos and about 2 of each individual part. So I took them all apart and gave them a good cleaning. Then using the best of each part I put one back together. I broke the magnetic circuit of the magnet when I took them apart so I had to 'Recharge' it.


Recharging the magnetic is just a matter of putting it on an even bigger magnet. To get a 'Bigger' magnet I built an electric magnet. You can get a full step by step guide to making one on Amazon, 'How to Build a Magneto Magnetizer'. I used mostly scrap steel and parts I had laying around the workshop. The only thing I had to buy was the 18ga copper wire for the coils. I woun,d each of the coils on the lathe and wired it up inside a metal junction box, just in case something went wrong.


There's nothing really tricky to rebuilding the NS2 magneto. I reassembled it the same way I disassembled it, easy because I took lots of pictures. Then, I recharged the magnet and slid it off the charger onto the base of the magneto, that way I wouldn't break magnetic flux. Put the distributor in and the cap on and it's done.


Now I just needed to test it. I didn't really have anyway of testing it so I built a test jig and hooked it up to my drill press. I took two pieces of angle iron and welded them together to form a tee. Then drilled and tapped two holes for the spark plug and four holes to mount the magneto on. I put a small vee pulley on the drive shaft and used that to drive it.


After I got it all built up and ready for testing, I just gave it a quick turn to make sure it would all turn over. The first turn of the drive shaft fired the spark plug. I got a spark just turning it over by hand! How cool is that.


Anyway here's a video...


So I have one working magneto now. The plan now is to use this one as a test bench to test each of the individual parts I have left over from the other two mags. I'll use the good parts to build a second one. After I have two mags tested and working I'll reassemble everything with Loctite and relube the bearings.


Gas + Compression + Spark = Bang


I’ve got one of three!


WTR : 55


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