So I charged my little battery with this cheesy charger for over 16 hours, but still no power for the neutral light or lights.  I thinking on going back to the old style battery - I know this one should work, but I have checked the grounds so its either more than that or its somewhere in the wires.  If the old style battery doesn't work then I will have to start troubleshooting the wiring.  It's 50 years old so I suppose there could be a problem somewhere. 

What i'd do now "& up to you to decide" on my dodgy ideas--is hook ya cheesy charger straight to the loom positive red & frame earth minus the battery & see if what you're trying to get working--now work. Should be a fuse not far from the battery, is it blown from all the experimenting or trying things. I guess the charger output is small but should get some sign of life. I've forgotten what we're talking but think 250 in which case nothing much runs off the battery, sorry was a 400 wasn't it but same horse. No neutral light. Speedo & tacho plus headlight run off the mag so motor running. Brake light & horn from battery plus indicators--Oh, & tail light in the US. Charger that small might struggle direct but indicators might just glow. Not sure so be careful. I've got a bigger old normal charger that would work doing that trick.

Sorry, CT1, so neutral light should glow of the charger as only 3 watt. We used to use 1.5watt sometimes.

Keep things straight here-
Battery only lights the neutral switch circuit, brake light, and horn.
All other lights power from key in position II, "nighttime," from the lighting coil portion of the mag.

I've used the battery you have before, and it doesn't like our Enduro's charging system. It will work OK but depending on mileage/time the battery will swell out and stop taking a charge. More miles you ride, more it well swell, less time it will take a charge, and vice-versa. It's just not designed for our style of recharging.

As Mark T said, the battery can short to the seat pan because of its height. I also encountered this playing with batteries to see what would work best.

You should take a hard look at the Tech Library wiring diagrams to chase voltages where they should be. Based on your comments you may have a problem with battery 6V getting to the ignition switch. 

When you put the acid in a wet cell battery, it immediately starts making voltage. It doesn't have to be charged to make voltage.
So it doesn't need a lot of voltage to make up the amount it is losing.
Normal charging VOLTAGE in the magneto models (with no load connected) is about 2 volts at idle.

When you receive a new gel cell, it has no or very little voltage/capacity. A gel cell has to be charged with the voltage for which it is rated. 
So, unless you use an aux charger, the magneto won't put out enough voltage to bring it up to its rating.



My opinion..... 

 

That makes sense to me DEET, and APEX. Only logical to me to keep what
works, a wet cell battery. Until there 
is something compatible and proven, that is what I will run in my '75. All You 
guys are giving great advice to Dan, as usual.
 

A lot of great information and I will pursue these avenues.  I'm not sure where that fuse is though, the hot lead appears to go directly into the wiring harness from the battery.

Is there a bunch of wires, sort of on top of the rear mudguard, oil tank side (rear lights plug in here)? They might be within a large rubber "boot". There may be two red female bullet connectors here and the fuse holder has two males which plug into these.

A few facts...

The "alarm batteries" being discussed are not "gel cells".  They are AGM aka SLA.  (Absorbed Glass Mat also known as Sealed Lead Acid).  The difference from a wet cell (stock type) is the electrolyte is captured in a glass mat and is non-spillable.  Both are still lead-acid battery technology. 

Advantage of wet cell is that when overcharged, they boil off the water to handle the excess energy  (which is why the vent tube needs to be routed carefully if you don't want acid damage) 

Advantage of AGM is obviously the "sealed" aspect, which can be a disadvantage in this respect.  AGM's tend to swell up and eventually fail if overcharged too much which is what Apex described.  I have had quality AGM's that have gone for years without failure...  some of the other "off brands" have failed during just one long high RPM ride.  Flooded batteries are much more tolerant of overcharging.

Both flooded and AGM batteries also tend to fail if allowed to discharge too far.

I want to clarify that no 6 volt battery will take a charge when charging system is producing 2 volts.  Stock or otherwise.  The charging voltage must be higher than the battery voltage for any power to flow into the battery.  Stock CT1 battery charge circuit doesn't start charging battery until 3,000 rpm according to Yamaha. There are service bulletins that describe how to "full wave" the CT1 charging system to keep the battery charged better during low rpm operation.  The caveat given is the higher charging will boil off the water faster so more frequent water checking is needed. 

My opinion based on my experiences...  I've had good luck with AGM's in the past...  Motobatt is a premium brand.  One thing is I won't run an AGM on a bike without a headlight voltage regulator.  While headlight and battery charge are different circuits, they are "intertwined".  These systems are brilliantly engineered and balanced based on the technology of the time...  a wet cell battery is the best you can get at absorbing excess energy and keeping voltages in check as a crude "voltage regulator".  In other words, stock early systems need a good wet cell in my opinion... and checking of the battery water often.  When you add a regulator to the headlight circuit, the need for a wet cell isn't as critical and AGM's perform fine.  YMMV.