Charging System (no pictures yet)

I have yet to hear anything positive about Lucas electrical systems, I’m beginning to understand why, but I’m still not convinced that if setup properly, and maintained properly, that I shouldn’t get enough juice to at least let me have a worry free ride.

When I first got the bike it had a small rectifier on it, as well as the zener diode and no battery.  I knew that if I wanted to get the bike running in order to find any issues that it might have that I’d be better off adding a battery and worry about charging problems later. This was the plan, but before long I decided for simplicity that I’d replace the rectifier and diode with a Mity Max unitl I’m more familiar with these parts.

I ordered the parts from British Cycle Supply and got them hooked up.  With a fresh battery and new Mity Max I was able to get a good spark when kicking it over.  This was enough to make me leave the electrical system alone while I worked on other issues, like cleaning the carb, etc.

Last summer while doing some work on the bike I re-wired it, long story short, fried the Mity Max.  Since I was already running with a battery I decided to go with a Tympanium unit instead of another Mity Max (financial decision).

After posting about my ride and reading some responses and checking out the manual I began my trouble shooting. With a charged battery I can start the bike without a problem, but if I check the AC voltage coming off the stator (this is a 2 lead RM21 stator, I think they’re only 100 watt stators) I’m only seeing about 6 volts RMS, and this is while revving the engine, not just at idle.  This leads me to believe that I have a bad stator, bad rotor, or both.  There are some steps that I’ve been given in order to narrow down the problem, one is to measure the resistance across the stator, the other is to check to make sure the magnets in the rotor are still good.

Since last summer I think I’ve got enough of the mechanical bugs out of the bike to be able to ride it. A short ride at the end of June reminded me that I still have to look at the charging system. After a 23 km ride the bike died at a stop sign, the battery, which had been breifly charged before the ride, was dead.  If I would have to guess I would say that I’ve been riding off the battery for most of the trip.

I unhooked the stator and measured the resistance across the two leads, 0 ohms.  Now while a stator is just a bunch of coiled wires, I was still expecting a small amount of resistance.  A couple other people from the Triumph Choppers list checked theirs and reported anywhere from 0.5-0.9 ohms.  This lead me to believe that I did in fact have a bad stator. My next step was to check the rotor. This can be done by pulling it off and hanging it from a large screw driver, if the magnets aren’t strong enough to keep it attached to the screw driver then it should likely be replaced. I assume you would rotate it and check each of the magnets. I got a message from Bep saying that a bad recifier can cause problems with the magnetism of the rotor, so it’s not unheard of for the magnets to get weak.

Checking the rotor proved difficult, impossible even, at least at the point of writing this.  The rotor won’t budge, it appears to be stuck on the shaft and I can’t get it loose.  Having hit this road block, and under the assumption that I had a short in my stator, I ordered up a new stator from BCS.  The stator arrived the next day, have I mentioned how much I enjoy living an hour from BCS, my first step was to hook it up to the multi-meter and check the resistance.  Much to my disappointment it read 0 ohms, the same as my old stator. Ideally to test a stator I would want to use something that measures inductance and not resistance, but I don’t have a meter that will do that.  So a little disappointed at not seeing what I expected I still decided to hook it up and test it.

As mentioned previously, the old stator was giving me 6 volts AC rms, the new stator gave me around 10 volts AC rms at idle, but approached 20 Volts AC rms when revving the engine.  The 10 volts at idle is a bit disappointing, by the time this gets converted to DC I’m looking at about 6.5 volts, not even close enough to run the bike or charge the battery. I’m seeing a marked improvement over the old stator but at this point I have to assume that the rotor is not working to its full potential.

A week or so went by and my brother arrived from Ottawa with his ‘69 T100, we tested some things out and replaced some wiring, but the bike never seemed to charge the battery. With the leads coming off the stator measuring up to 40 volts AC, when not connected to the Tympanium, I ruled out a faulty rotor.  We had the benifit of using my brothers Mity Max to see if the issue was with the Tympanium, sure enough, with the Mity Max in place I was getting over 12 volts, into the mid teens coming off the DC side of the Mity Max.  I ended up replacing the Tympanium with a Mity Max and haven’t had a problem keeping the battery charged since.

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