There is no aspect of the Triumph line of motorcycles as badly maligned as the "Lucas, Prince of Darkness" electrical system. Many people actually think it's bad, not knowing that the real reason we've always fondly insulted Lucas electrics is really to keep the prices down on our favourite mounts.
Guess what! The Lucas electrical system is actually a very well- thought out, quality-built selection of components, designed to be compact, efficient, and adequate for the service for which they were intended.
They were once better. Sparks for almost all British motorcycles were at one time supplied by elegant little high-tension magnetos, build by Lucas, which were incredibly reliable even when rudely mistreated. Low volts were provided by a full-on DC generator, with a floating-points mechanical voltage regulator varying field voltage according to sensed output requirements. It was an elegant system, but subject to vibration problems, (the regulator, mostly) and judging by the quality of the construction, was very expensive to build.
Also to replace. The mechanical voltage regulators had a bad habit of taking the generator with them when they went, and during the days that these bikes were available in the 2 to 300 dollar range used, a fresh generator and regulator often cost more than the motorcycle was worth to replace. There was a lot of riding sans lights in those days! And lots of cheap Britbikes with, unfortunately, no lights.
In 1953, Triumph introduced the Speed Twin with a "new" electrical system involving a crankshaft-mounted alternator, and coil ignition, using points, coil, condenser, and thus requiring no expensive magneto. Best of all, the system had no mechanical floating points regulator, and was much less susceptible to vibration and burning itself up. The extra reliability inherent in this system quickly found acceptance by the average Britbike enthusiast. This evolved, if so few changes can so be called, to the system we enjoy today. If you are having trouble with your electrical system, it will usually be found to be fairly easily and cheaply fixable.
What all this tells you is that, if you just can't get the juice you need, you can make some changes, to components newer, stronger, or both. But in most cases, troubles with insufficient output can be fixed a little more easily than this.
So, the first fix we'll discuss is what to do in _this_ situation. Obviously, how you got there is by running your battery down - drawing more from it than the alternator can replace - until there wasn't enough left to continue. Sometimes just turning the lights off will get you home. Sometimes, you'll have to get some juice into the battery before continuing. I've been in this situation more than once, and had to bum a boost from a car owner. In extreme cases, just hooking up to the battery of a non-running car, with a piece of speaker wire, will boost enough for ten or 15 minutes of running - sans lights, of course. So you just hook 'er up, and go back and have another beer or two, by which time the bike will start, and you'll have _some_ time to make it home. Best without lights. It's better in these cases to hook up to a vehicle that's been left running - the charging system voltage is higher than that of a still battery - 13.8 Volts instead of around 12 - and your battery will charge considerably better. But 15 minutes or so of just being connected to a properly charged battery will do wonders. I make a point of including 5 or 6 feet of speaker wire in my toolkit for just this purpose. - Be REAL CAREFUL about polarity! Reverse=charging your battery will kill it dead, and probably finish off your charging system at the same time!
If you ever find yourself in this position, however, you know you've got something to fix. Let's look at how.
First, check your charging system voltage. Before starting the bike, check your battery voltage with a voltmeter. Then, start the bike up, and check it again, with the engine running at about 1500 rpm, and the lights off. This is the charging voltage, and it should be higher than the basic battery voltage. 13.8 would be nice, but in the real world, even 12.8 is decent. Any less than that, and you know your battery's never going to get a decent charge. Now, turn the lights on, and check it again. If the voltage drops below 12 here, you know that your battery's going to be in a state of net discharge when you're running with full lights.
Another consideration here is Just how good is your battery? Since we don't use our battery for starting, it can be in pretty bad shape without giving any indication. Check the connections, and the fluid level. Top up with distilled water if necessary, and allow to stand awhile before charging. Put a small trickle charger on it overnight, and then the next day, connect a taillight to it and see how long it takes to run it down. Since the original Brit specs called for keeping parking lights on overnight, you can expect a good battery to keep the light burning for 10 or 12 hours. I wouldn't run it right down, but if on checking after only a couple of hours, you find it's no longer burning, hike off to your local KMart and git you a fresh one - the Tri battery is a fairly common one, and most places that sell MC batteries stock it. Then let's continue with checking the charging system.
Another obvious improvement is simply cleaning and tightening all your connections in the charging system. Locate the connectors from the alternator wires as they leave the primary chaincase. Pull these apart and inspect them for shiny. Clean them as lightly as possible, since they're cadmium plated and you don't want to take off the plating if you can help it. Don't forget also to clean the insides of the tubular coupling sleeves - 8 surfaces altogether. Then do the same for the spade connectors to the rectifier. Be sure also to clean the rectifier's mount to ground. In fact, there's nothing wrong with borrowing a page from J.A. Pan & Co. here, and running a second red ground wire between your major components - from the rectifier mounting bolt to the battery positive terminal, instead of relying on the chassis to carry the current. Copper is always a better conductor than steel, anyway.
If charging is a problem for you, you may want to replace your probably-dried-out selenium rectifier with a Radio Shack replacement. Bridge rectifiers being a common element in electronics, RS supplies a 10 and 20 Amp replacement in modern solid-state silicon version for less than a 10 dollar bill. Be sure to mount it so that it can bleed the heat it produces into an aluminum plate which you cleverly build as a mount. The earlier RS bridges had spade connections, but the later ones seem to be straight wires, so you'll have to solder the wires on. The terminals are marked + for the one you'll ground, - for the one you'll connect to the battery -, and the ones marked AC may be connected either way to the output from the alternator. Also, be sure to "heat sink" the heat from the soldering iron by using your third hand to clamp a pair of needle nose pliers to the component side of the soldering site. Once you're done, you'll likely find that this little improvement makes quite a difference.
If your system voltage is still low after all this, you may want to try disconnecting your Zener diode. The purpose of this baby is .... wait for it ....... to _dispose_ of excess voltage, so that your charging system won't overcharge your battery, burn out your lights, etc. Although hilariously funny to those who find themselves without the juice to get home on dark nights, this is actually a truth for some. I've had batteries boil with the Zener disconnected, even with the lights full on, so be sure to check your charging voltage after you've replaced the diode, and find out if you need to disconnect the Zener. Theoretically, it shouldn't draw any current at all below it's "knee voltage" of 13.8 or so. The more savvy may want to put an ammeter in the circuit to the Zener, and see if there's any current draw below this voltage.
There is also a solid-state device on the market called a Typmanium voltage regulator. It's actually a regulator/rectifier replacement, modern electronics, and is an excellent thing to use if the simpler process described above runs into snags, such as if you need a new Zener. Here's the British Cylcle Supply listing:
332-104/A TympaniumPowerControl uni EA 75.40
It seems to me that a major consideration should be the difference
in quality. After all, there is a particular old-world quality in the
construction of these bikes, particularly in the pre-OIF's, and it
really riles me to see people flocking to spend big bucks on replacing
that lovely cadmium-plated steel and shiny machined cam, weights, etc.
with a not-particularly-brilliantly-crafted piece of fiberglas and
epoxy with a few hunks of solid-state sealed within.
The standard Lucas components are very nicely made, are after all
the stock ones - we _are_ restorers, aren't we? - and with a mininum
of maintenance, will give good service for the life of the
motorcycle. Furthermore, there are a number of advantages to keeping
the standard points in there where they belong:
The same applies to converting to Lucas Rita. Made later, made
much tackier, not correct anyway. And even more expensive.
Keep on Trumpin'!
Click here to go there
THE COURT OF LAST RESORT
391-47205 stator,2 wire,RM21,std.12 EA 158.50
391-47204 stator,3 wire,RM19,120 Wa EA 173.50
391-47244 stator,3Phase,180 Watt EA 162.54
391-47252 stator,3ph,'79&80 Tri ks EA 172.54
391-47197 stator,5 wire,RM19,for ET EA 0.00
391-47105 stator,RM13 alt,3 wire EA 135.00
391-465998 stator,RM14 EA 0.00
391-47127 stator,RM15 alt,3 wire EA 150.63
391-47209 stator,RM20,early Triples EA 147.42
391-47194 stator,sing.phase,180Watt EA 219.40
391-47239 stator,sing.phase,180Watt EA 182.07
391-465969 rotor,RM14 alt,3.250"od EA 0.00
391-466125 rotor,alternator,2.75"od EA 90.00
391-60600684 rotor,alternator,late,2.9 EA 194.18
2) The Ignition System
SOLID STATE CONVERSTIONS
331-02 Boyer ign,TriBSA unitTwin EA 169.00
391-54415746 advance unit,c.wise,5deg. EA 145.00
391-54416405 advance unit,ccw,10degree EA 0.00
391-54416150 advance unit,ccw,5 degree EA 85.00
391-54418404 advance unit,ccw,5 degree EA 0.00
It seems to me that a major consideration should be the difference in quality. After all, there is a particular old-world quality in the construction of these bikes, particularly in the pre-OIF's, and it really riles me to see people flocking to spend big bucks on replacing that lovely cadmium-plated steel and shiny machined cam, weights, etc. with a not-particularly-brilliantly-crafted piece of fiberglas and epoxy with a few hunks of solid-state sealed within.
The standard Lucas components are very nicely made, are after all the stock ones - we _are_ restorers, aren't we? - and with a mininum of maintenance, will give good service for the life of the motorcycle. Furthermore, there are a number of advantages to keeping the standard points in there where they belong:
The same applies to converting to Lucas Rita. Made later, made much tackier, not correct anyway. And even more expensive.
Keep on Trumpin'!