When is there draw on the battery?

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Apr 2, 2008
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My riding of my '73 850 consists of going out at least once or twice per week on twisties for 50 to 100 plus miles. If I have the stock system with capistor and points, will a gel cell battery need to be disconnected (say at the fuse) between rides to keep from pulling the battery down. I realize that many folks would have a pigtail for a charger and just plug it in between rides but my garage is a few blocks away and has no electricity.

If my current system with capistor would drain the battery, is there an upgraded system that would not draw on the battery while sitting between rides?
If your battery goes dead, there is something wrong somewhere. Check with an ampmeter if current is flowing when the motor is not running and the ignition switch is off as well as any lights. If there is current flowing (even a few milli amps) start disconnecting things until the current drops to zero, the last thing disconnected is either the problem or it is in that circuit so follow the wire and disconnect anything in that circuit.

If the capacitor is old it wont hold its charge and will draw from the battery over time, it is permanently connected so does this with the ignition off. That said my capacitor is an orginal and after a 6 month layoff it started 1st kick with a 10 year old gel that does not get charged at all.

The classic failure is the rectfier.
If you haven't metre etc, just pull the fuse push the wires through the holder to expose the ends and touch them together. You shouldn't see a spark.
Now for the short term if you want to use your Commando after each trip remove the fuse. However, try not to delay the repair.


Your gel battery, provided that it is in good condition and not too small should be able to be left for months, and still have enough charge to start the bike on points?
The 2MC starting capacitor is useful as it allows starting when the battery is flat. If it is old, as kommando said, it can drain the battery.
I believe the life expectancy of the 2MC unit according to Lucas, was around 1 year or even less in warm climates! Yet many do last for years.

So I suggest you try disconnecting the 2MC by removing the (Red) ground wire, but not the (2-3?) Brown/Blue wires, unless you re-connect all Brown/Blues together?

If the battery still goes flat after a few days with the 2MC disconnected, then the problem as cash said, is likely to be with the rectifier.
Cash, I have a meter so what exactly is the test with meter for the rectifier?

Also, is there a test with meter to see if the capistor is functioning correctly?
Yellow_Cad said:
I have a meter so what exactly is the test with meter for the rectifier?

Use the meter on Ohms in place of the battery and bulb: http://rocbo.lautre.net/technique/norto ... p/138.html

Yellow_Cad said:
Also, is there a test with meter to see if the capistor is functioning correctly?

You could check if there is an Amp or Milliamp drain on the battery through the 2MC capacitor (ignition off)?
And if there is, whether it stops when the 2MC is disconnected?
The easiest way I would think would be to disconnect it and see if the battery stops discharging as quickly?

To check if the 2MC will hold a charge for a reasonable period of time I disconnect the battery (by removing the fuse - ignition off) and then leave the bike for a couple of hours, after which time I would switch the ignition on without reconnecting the battery and if I saw the charge & neutral (MK III) warning lights flash on briefly, then I would know the 2MC was OK.
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