I think it's the battery, so it's probably...

MattIn11225

MattIn11225

New Member
Hi, total newbie here, and I'm sorry if I'm rehashing. My 1972 CB350 Twin, which I've had for about two weeks, has been having a harder and harder time idling and keeping the lights in working order. The bike will intermittently stall out at stops, and will do so more often if I've got an indicator on. Over the past week, the indicators have stopped flashing regularly, either staying on steadily or flashing on occasion. Indicators remain steady if the headlight is on. Today, I noticed the starter is very sluggish, the neutral light was dim, and then nothing from the starter. Bike usually kicks off of one go, but I had to let it sit for about 20 minutes before it would turn over and come to life.

I'm in Brooklyn, so the riding is mostly start and stop with little time spent in the 4.5k+ rev ranges. My though is that the battery is probably on the old side, and has not had much of a chance to get charged while in low revs. I'd like to see what your thoughts are.

If this sounds like a battery issue, what options are best? Replace battery, and if so, what would be a good drop in option? Could it be something else?

I set both the point gaps and the timing over last weekend, and the idle went from pretty rough to smooth. Have I missed any symptoms that I should add?
 
A battery is cheap 30-40 bucks. The part number is 12N12A-4A-1 but double check before buying. You may have a problem with the charging system/stator. If you replace the battery and in a couple of days you have problems then that's probably it. You can take the guessing out of it and just take it to a shop.
 
Just don't use anything but first gear, it will be revving high enough to keep charged.
Best modification would be fit combined regulator rectifier plus dispense with the wiring from alternator to handlebar switch and back
 
Replacing parts is an expensive and ineffective way to diagnose your problem. Diagnose FIRST, then replace what's needed.

If your charging system is not up to snuff, a new battery will not fix it.

Start with your battery fully charged. Get a small "battery maintainer" at any auto parts store, (about $30,) and charge the battery till you get a green light. Let the battery "settle" for 24 hours. You will also need a multimeter, which you can get at the hardware store for about $20. Check the battery's voltage. It should read at least 12.8 V. Then take it back to the auto parts store and ask them to load test it for you. Replace it if need be.

If you need a new battery, you will need that battery maintainer to give a conditioning charge to your new battery before you put it into service. Don't just put it in the bike for the bike's charging system to charge it unless you are willing to have degraded service life from the battery.

Now, with a fully charged, known good battery in your bike, check the charging system. Start the engine. Check the voltage at the battery. It will be around 13 V at idle, (which isn't really enough to charge it.) Rev the engine to about 2,500 RPM. The voltage should go up to 14V or higher. If you have an AGM type of battery, charging voltage above 14.3 V will shorten its life. A lot of these bikes will put out 15 V at high revs, so a flooded cell type if battery is better.

If your charging voltage does not come up to spec, you have to determine whether the problem is your voltage regulator or your stator. You do that by disconnecting the stator from the voltage regulator and measuring the voltage with the engine running using an AC range on the multimeter. You will she higher voltage as the engine revs higher. It should show something like 40 VAC at around 2,500 RPM. Check your service manual for what the voltage should be.

Oh, you don't have a service manual? Get one fer cryin' out loud! (Do a search on the Web, and you should be able to find one you can download.)
 
AlphaDogChoppers said:
Replacing parts is an expensive and ineffective way to diagnose your problem. Diagnose FIRST, then replace what's needed.

If your charging system is not up to snuff, a new battery will not fix it.

Start with your battery fully charged. Get a small "battery maintainer" at any auto parts store, (about $30,) and charge the battery till you get a green light. Let the battery "settle" for 24 hours. You will also need a multimeter, which you can get at the hardware store for about $20. Check the battery's voltage. It should read at least 12.8 V. Then take it back to the auto parts store and ask them to load test it for you. Replace it if need be.

If you need a new battery, you will need that battery maintainer to give a conditioning charge to your new battery before you put it into service. Don't just put it in the bike for the bike's charging system to charge it unless you are willing to have degraded service life from the battery.

Now, with a fully charged, known good battery in your bike, check the charging system. Start the engine. Check the voltage at the battery. It will be around 13 V at idle, (which isn't really enough to charge it.) Rev the engine to about 2,500 RPM. The voltage should go up to 14V or higher. If you have an AGM type of battery, charging voltage above 14.3 V will shorten its life. A lot of these bikes will put out 15 V at high revs, so a flooded cell type if battery is better.

If your charging voltage does not come up to spec, you have to determine whether the problem is your voltage regulator or your stator. You do that by disconnecting the stator from the voltage regulator and measuring the voltage with the engine running using an AC range on the multimeter. You will she higher voltage as the engine revs higher. It should show something like 40 VAC at around 2,500 RPM. Check your service manual for what the voltage should be.

Oh, you don't have a service manual? Get one fer cryin' out loud! (Do a search on the Web, and you should be able to find one you can download.)
Click to expand...

Hey man, This was all such valueable information. Having a similar problem on my CL350 currently that it runs good at high RPMs but will not sit at an idle properly and dies out in neutral at idle (video: http://www.youtube.com/watch?v=3bVMemLNWWk). I was wondering, you said it is either voltage regulator or your stator, could it be the rectifier or is this not a symptom of that? I simply can not figure out what is wrong!
 
spectacularspecimen said:
I was wondering, you said it is either voltage regulator or your stator, could it be the rectifier or is this not a symptom of that? I simply can not figure out what is wrong!
Click to expand...

My instructions are a bit generic and intended for bikes with a regulator/rectifier. Most bikes have both of those functions built into a single device. I don't know specifically whether your bike has a separate rectifier or not. I don't keep that in my head. Generally, I can SEE whether they are integrated or not when I work on the bike. <G>
 
I have not tried either of those things yet.

Could a carb sync or the idle screw be effecting it dying while idling? It runs great otherwise but just will not stay on. Thanks man!
 
Absolutely, you'll want to check your idle adjustment and fuel screw. Turning the idle screw in will open the butterfly allowing more air into the mix. Turning your fuel screw out will allow more fuel to flow through the pilot circuit. Check the shop book for the amount of turns out on each for a baseline to start. I'd suggest cleaning your carbs and paying special attention to the pilot circuit, removeing the pilot jet and fuel screw blow it all out, check for crud...
 
The only problem with ADC is he uses very technical language that a layman would have trouble understanding. 8)
 
I've been told that the words he speak are gospel.

bradj said:
rule of thumb if teazer and adc are kool with it take it as gospel, so the real question is are you ready to testify
Click to expand...
 
John, the idle screws and fuel screws are completely different things adjusting idle screws holds the butterflies open, the 'increased fuel is a result of higher airflow.
The fuel screws can increase fuel supply without having any effect on airflow
OP, you have separate reg/rect, it's worth getting a combined unit
 
Sir, you are correct, I just read my post and it didn't make sense to me. I have edited it for any poor suckers that might read it in the future. :p
 
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