Is the little blue can necessary

On my 73 850, my little blue can is shorting out. My local Norton supply house says to just do away with it if I use a battery. I do use a battery (gel cell) but before just by passing the little blue capistor, I wanted to run it by the folks on this board. If I do do away with it, is it OK just to leave the wires unplugged since they are insulated connectors?

Yes, as long as you have a good battery.

Ken G.

O.K., I'll bite. What and where is / are this "so called" blue can? :?

It is just a capacitor meant to smooth out the DC from the rectifier allowing a stock Norton to run without a battery. I ran my 69 "s" a few times without a battery, but a Commando with a Boyer or any other electronic ignition may not work at all without a battery because of the greater current drain. So like others have said, you can do away with it. When I wire a bike from scratch, I never put one on.

Jean

If an owner decides to disconnect the 2MC capacitor (and they are not always fitted) just remember to reconnect the Brown/Blue (or Brown/White - early models) wires together.



2MC info: http://www.gabma.us/elec/lucas_2mc.pdf

The blue can capacitor is not needed in normal operation. It is used for emergency starting if the battery dies. The (flat) battery is disconnected first. ~~~~ I believe this is all in the riders manual. ~~~~~~

The Boyer does work with the blue can only (at least on my combat) but you'll need to kick it like you mean it.

Don't pay a ridiculous price for a New Old Stock Lucas capacitor. These have a shelf life so one that has been stored for 35 yrs is nearly as bad as the ones in use. Either find a newly produced one if there is such a thing or buy one of the "replicas" that use new capacitors. The capacitor itself should be rated higher than just 15-20V - Something at least 35 or 50V would be good. If you have a positive ground bike it is useful to know that many commercially available electrolytic capacitor "cans" have the negative side of the capacitor connected to the aluminum shell, so you'd have to put some large heat shrink tubing on it or find a way to insulate it. You can also carefully dissect and hollow out the original Lucas can and hide a modern capacitor inside. This technique is frequently used when restoring old radios to keep them looking authentic inside.

Russ

MrFastback said:

O.K., I'll bite. What and where is / are this "so called" blue can? :?

Click to expand...

It's the Lucas 2MC capacitor.
You can eliminate it. I have. They have a life of about 18 months, and nobody ever seems to swap them out. i don't think new Lucas ones are available, but replacements using Phillips (or other) capacitors are available. This one from ebay is $20
http://cgi.ebay.com/ebaymotors/Triumph- ... QQtcZphoto

But you can substitute a Radio Shack 4600uF (or larger) capacitor for about $5.

For more really good info see R F Whately's article http://www.gabma.us/elec/lucas_2mc.pdf

L.A.B. said:

If an owner decides to disconnect the 2MC capacitor (and they are not always fitted) just remember to reconnect the Brown/Blue (or Brown/White - early models) wires together.

Click to expand...

With the key off, I show about half continuity to ground from the bike side of the fuse holder with the blue can hooked up. With the blue can completely unconnected, I show no continuity to ground. With the blue can unconnected but the Brown/Blue wires connected and the ground left unconnected, I show again half continuity to ground.

Could anyone please give me some idea of what is happening here? Much thanks.

Yellow_Cad said:

With the blue can unconnected but the Brown/Blue wires connected and the ground left unconnected, I show again half continuity to ground.

Could anyone please give me some idea of what is happening here?

Click to expand...

Then the fault appears to be somewhere other than the Blue can (2MC)?

Disconnect the two (or more?) Brown/Blue wires from the 2MC, and do the continuity to ground (Ohms) test on each Brown/Blue terminal. That should at least show whether the fault is on the battery side of the 2MC, or between the 2MC and the ignition switch?

What happened when you did the check with the Zener and/or rectifier disconnected?

L.A.B. said:

Then the fault appears to be somewhere other than the Blue can (2MC)?

Disconnect the two (or more?) Brown/Blue wires from the 2MC, and do the continuity to ground (Ohms) test on each Brown/Blue terminal. That should at least show whether the fault is on the battery side of the 2MC, or between the 2MC and the ignition switch?

What happened when you did the check with the Zener and/or rectifier disconnected?

Click to expand...

Les and others, thanks for your help on this. For a while, I was flying blind as I didn't know exactly what results to expect from what tests. It all sort of makes sense now.

The half continuity to ground didn't change with first the zener diode disconnected and then with the rectifier disconnected so I could rule those two out. When I was testing and reconfiguring the little blue can wires (and getting a little puzzeled in the meantime), I found one of the Brown/Blue wires (there are actually three wires on two connectors) rubbed bare. I repaired the skinned wire, reconnected the little blue can, and all is well again. I do appreciate the help and the things I learned for dealing with those three components in the future. I will probably convert soon to a solid state regulator/rectifier.