DIY MZ alternator rotor

smegballs · World Chat Champion Joined: 28 Oct 2007 Karma :

I've decided that I want a self contained ignition system on my MZ rather than having a battery dependant system. After seeing how good the RXS is regarding sparks, having kick and spark ignition seems a very good idea!

If the MZ was a permanent magnet alternator system I could do this quite easily by removing the stator and winding a wire around the outside of the stator coil. Then with this ignition coil run one end to the points and one end to the earth. This would have the ignition circuit working as a points magneto system as found on lawnmowers and the like...

The problem is though that the MZ is a field regulated alternator which means there is little to no residual magnetism without a battery connected. If I was to somehow make a rotor body and fix strong permanent magnets to it would this convert the alternator to a functioning PMA? The MZ runs an internal rotor design.

Another possibility would be to use something like the tacho take off on the other end of the crank to run a small DIY alternator (possible axial flux design as easy to make) and use this as the magneto to be fed back to the points.

Ideas BCF?

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Or go the whole hog. Mount a car alternator on the front of the engine, mount a pulley where the standard alternator goes and join the two using a belt.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
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Blau Zedong · Banned Joined: 26 Jun 2006 Karma :

You can't do it with the stock generator setup, not a chance. Also note that points systems powered by a generator (rather than being "active" i.e. across the main battery) tend to have poor low speed performance, often needing two sets of windings to create an effective spark across the rev range. The only way to do it would be to fit a fancy ignition like a Powerdynamo or similar.
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smegballs · World Chat Champion Joined: 28 Oct 2007 Karma :

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Fat sparks aren't necessrily good ones these days.

The spark off an MZ-b magdyno system is so thin and blue it is almost invisible, this is actually due to it being so powerful and using an extremely high voltage.

I see where you're coming from though. My CDI powered H100 never fails to make a spark using a single coil winding and comparatively shitty rotating magnets.

You could probably transplant the whole RXS/H100 single wire ignition system onto an MZ by means of re-drilling the stator plate and doing some sort of jiggery-pokery for the flywheel. They don't have any ignition advance so timing would be relatively straightforward.

Trouble is, it would leave you with ultra shit, 6v direct lighting.

EDIT: You do know that a standard, 9v PP3 battery (as fitted to smoke alarms) is sufficient to power up the field coils? Rex (the guy with the SU carbed MZ) has some PP3 stubs attached to the field coil wiring. If he gets a flat battery, he takes his emergency PP3 battery out of its film container under the seat, clips it on, starts the bike then unclips it.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

bladerunner · World Chat Champion Joined: 09 Sep 2006 Karma :

PP3 battery idea should work fine..however not sure about the car alt idea as they usually need battery voltage to generate the magnetic field to start with..which means back to the battery idea!!
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smegballs · World Chat Champion Joined: 28 Oct 2007 Karma :

A motoplat would work well for the ignition bit of the affair.... I think they use motoplats or something similar for the ignition on the racers....

I've thought of getting a car alt on there before but I'm not sure how to mount it on an MZ due to having no frame members at the front. I havent had a proper look at siting to be honest thought.