electrical problem

wondering if anyone has experienced this... have a 72 commando while at idle if I turn on the headlight, use the brakes or turn signals she wants to stall and cut out.
While riding as long as the RPMs are above idle she'll keep running. Any thoughts or suggestions on the troubleshoot? much appreciated

battery charging - when I got my '75 if I ran a fully charged battery, after a little while turning on the sugnals/ indicators would make it cut out at idle. Check battery charge and stator output.
That's my guess, anyway

gory said:

battery charging - when I got my '75 if I ran a fully charged battery, after a little while turning on the sugnals/ indicators would make it cut out at idle. Check battery charge and stator output.
That's my guess, anyway

Click to expand...

I agree with this.
Same symptoms I had and solved with new battery.
If battery older than two years I'd have it checked.
If newish battery I'd check alternator output.

thanks! that was going to be my starting point. which begs another question.
i hear pros and cons of Gel & AGM battery types... who has had the best experiences and which manufacturer and model #?

jcor said:

wondering if anyone has experienced this... have a 72 commando while at idle if I turn on the headlight, use the brakes or turn signals she wants to stall and cut out.
While riding as long as the RPMs are above idle she'll keep running. Any thoughts or suggestions on the troubleshoot? much appreciated

Click to expand...

1. You have a flat or faulty battery.
2. Any reasonable quality battery will do the job. Lead/acid is most suited to the standard charging system. 13.8-14.2v charging voltage.
3. Put a volt meter across the battery while runing and tell us the voltage at 1000 rpm, 2000rpm and 3000 rpm.
4. Have you changed any bulbs lately ?

A good battery is a must, not just an adequate one.

There is a charging port on the bikes for a reason. If you run the lights all the time, like you should, the standard charging system will usually need some assistance from an outside source, hence the port.

You are showing that the charging system is working but the battery is not keeping up. You can take it to any auto parts store for a free load test.

If you get a new battery remember, bigger is not really better unless the AH of the charging system matches the AH of the battery.
the 130w stock stator is good for a 9 of 10 ah battery. 12ah will work but you would be pushing it. Many people like to put as big a battery as will fit and cannot figure out why it won't charge well. A 14 ah battery needs more than the 130w stator can provide. This is an instance where external charging is needed. 130w / 12v = 10.8amp.

Remember, the bike lives off the battery not the stator. The stator feeds the battery not the system.


Best advice, get a 180 or 200watt stator and a 14ah battery and don't look back. Some will suggest a 3 phase system, overkill at bast unless you have electric start.

For much added dependability ditch the zener and reg/rec unit for a Matching Podtronics unit.
I say matching because they come in 130, 180 and 200 watts.

thanks you guys are the bomb!
I'm going to try a Gel battery wish me luck or say I'm crazy

Gel batteries are cheap, but supposedly they don't hold up with vibration. Look at Wiki. AGM are better in that respect, but probably cost more.

Let us know in any case. I got the AGM from Clubman, not that I'm trying to push his products, but it's a name brand battery.

Dave
69S

Take a look at Shorai batteries.

Snorton74 said:

Take a look at Shorai batteries.

Click to expand...

OldBritts has them. 9AH fine for any Commando without a starter.
Very light and long lived and an easy installation.
Pricey but should last at least 6 years.

Lithium-Iron Replacement Batteries by Shorai
Old Britts is offering two of the excellent Shorai Lithium Iron batteries to replace the stock lead acid batteries normally used in Commandos. We stock a 18 amp hr battery to replace the battery used in the 1975 MK3 battery and the 9 amp hr battery used in the other Commandos. We recommend using a higher amp hour battery than the stock lead acid battery to be on the safe side. For this reason we find the 18ah battery will replace the 14ah MK3 battery, but feel that combining two 14ah batteries in parallel, giving 28ah, is the best for the MK3 or the Old Britts starter.

Some of the features of these batteries are:
•No more dead batteries. Holds charge for one year without maintenance.
•Twice the service life of lead-acid batteries on average.
•Drop-in replacement for your OEM battery.
•Military spec Carbon Composite Case.
•Faster cranking for better starts.
•Ultra light. One fifth the weight of lead-acid batteries on average.
•Super-fast recharge rate.
•SAFE - No explosive gasses during charge, no lead, no acid.
•Environmentally friendly,
•Japanese engineering and components.

•A. The lead acid 9 amp hour battery used in most pre-MK3 Commandos. Weight 6 lbs.
•B. The Shorai replacement 9 amp hour battery. Weight 1.5 lbs.

Old style Boyer electronic ignitions don't do well at low RPM and my bike used to die with any kind of load at idle. Usually at stop lights with traffic behind me! I put a Pazon on and bike will idle all day at 800 RPM with same battery and alternator! Happiness is being able to take your hands of the throttle at stop lights!