Total Motorcycle Community Forums

TechBMW wrote:You can get a $25 multimeter from sears and it will be useful for the duration of its life. You bought this old bike ... might as well give it a go.

All you have to do is take a multimeter (or simple voltmeter), start the bike up and check to see if the battery is reading over 13.5 while running. Very simple ! Maybe you even have a friend that will let you borrow one?

Well, I can't really start the bike...And if I could, it doesn't idle. :p

And since it ran a few days ago...But won't now that the battery is dead, doesn't it seem like the bike is ok?

If you have a multi-meter the first thing I would check is the resistance in your battery cables and connections to your stator and starter. A high resistance value is bad and the whole system will run poorly. Corrosion can and does happen inside a wire where you cannot see it which causes all types of problems. As an RV Tech I have seen it many times in older vehicles.

[ Note: Disconnect your battery first]

in simple terms, they're trying to discover if your battery is buggered, or the bit of the bike which recharges it

Before investing in another "new battery" I'd invest in a charger.

Theirs no way for a new battery to loose the ability to hold a charge in two days.

Besides a charger is a necessity to a bike owner for storage and freshening up of the battery.

Older bikes have a crummy charging systems and it's good practice to put the bike on charge at least on night a month to prolong the life of the battery.

Good Luck!!

And keep us Posted!

Mike Haverhill, Mass

Wargasm wrote:Still dont' have my 360 running. I've put a lot of time, and money into it now (well, a lot for me).

Got a new starter put on, and a whole new shifter column deal...The guy at the shop said the electric start works fine, but that my battery didn't have enough of a charge to start it. I manage to kickstart it, and drive it around for a bit, before it dies, and cannot be restarted. I don't know much, but it sounds like a stater issue to me...Just a few hours ago though, I fully charged the same, new battery, but it still struggles and will not start...What do I do now? I'm sick of taking this thing into the shop.

I have a CB360 and had a CB350.

FIRST: Check fuses and wire connections. Loose connections are common on these old bikes.

The charging systems are weak. The weakest point is the rectifier. You can replace it with a generic full wave rectifier from radio shack. Anything above a 20 amp rating will do, but I would get a 50 amp rating so it runs cooler . The next bad area is the voltage regulator. The alternator does not have brushes, it has permanent magnets. The regulator simply shorts the system to ground above 15.6 volts. A volt meter is necessary to check it. The regulator is harder to find. A good Googling is in order.


The alternator has 2 charging circuits. 2 coils in the alternator provide ignition power and a slow charge to the battery. The other 4 coils are for lights. If the wiring to your handlebar switch are disconnected or loose connection, yuor alternator will not put out full volts.

Additionally, you do not get much charging below 4k RPM. If you run around at low RPM all the time, the battery goes pretty quickly.

You really need a wiring diagram. I have a 76 diagram. The older ones are a little different as Honda did away with the on/off switch for the lights.

The coils could be bad, you will need a manual to tell you the resistance.

Finally, your magnets could be weak, with replacement the only option. I don'y know how to check them , but I don't believe this is a common problem.

If you dont mind working with electronics and solder guns, you might even be able to fab a regulator. There are a number of monolithic regulator IC's available online, you would need to check one with the correct current rating. Normally the current rating for your rectifier is the what the rating is for you regulator. If you'd like something more sophisticated, a hi-wattage DC-DC converter should work just fine too.

I'll try looking up some resources, and get back on this.

%The regulator on these bikes is just a Zener Diode. No manipulation of the field strength as the alternator is pemanent magnet.

You could probably find a Zener with the rating that is needed and a good heat sink.

I thought about even getting a 20 amp battery charger and gutting the transformer. A 20 amp charger is cheaper than the OEM parts and would probably work as well...

I just went through a similar situation with my '74 cb360. I couldn't start and then I was running on one cylinder. Anyway, I'm running perfect now after a full carb clean and a new rectifier (used for about $30). I'm not positive this info is correct, but I was told I probably fried my rectifier by charging my battery while it was still hooked up to the bike - Someone want to confirm that for me? - just wanted to warn you so you don't cause another problem while chasing the first one like I did. Anyway, my past experience with this bike tells me that you can kill a battery pretty quick by repeatedly trying to start it without success and you won't get anywhere in your diagnostics by trying stuff with a dead battery. Get that thing charged fully and then tackle the problem.

As log as you charge with a trickle charger, you should be able to charge the battery on the bike. The battery should sink momst of that current anyway, and if the rectifier blows with the marginally higher voltage its probably on its way out anyway.