Topic: Odd electrical gremlin in my CB350 (Updated)

[Raul CB750K1]

Yesterday I took a long ride on my CB350 to the DMV inspection station -the bike is not road legal yet but I don't have a trailer nor do I want to pay for one when it is a matter of a 20 minute ride. The bike didn't pass the inspection for some paperwork variation on the tire size, very long subject to discuss here.

The battery was freshly charged, as it used to discharge during the test rides after the restoration. I put the blame in the fact that I had to extensively use the starter, that the bike didn't ride long, and that a new battery needs a few charge-discharge cycles to get its full capacity.

One day I was taking some pictures with the bike idling and it just stopped. When I tried to start it the lights were dim, the battery was empty, but fortunately the CB350 has a permanent magnet so I could start it with the kickstart. From that day I suspected that the aftermarket H4 headlight was draining the battery, as the original lamp was something like 35 or 40 watts.


I did a check at the schematic and it seems that the alternator has three windings. One of them is used for "day" riding, to keep the battery charged and to run the ignition. The other two are for "night" riding, only switched on when the light is switched on. According to the specifications, the alternator gives only 100 W, pretty scarce when the low beam is 55 W.

Anyway, yesterday it was all road riding, so the alternator was revved high and therefore should be giving all its juice. When I returned home, again the bike stalled and the light was dim. So I just switched the light off and kickstarted it back to life. Then, the headlight would bright up, clear sign that the alternator is doing its work. So why is the battery discharging? The only thing that comes to my mind is that the lamp is taking more juice that what the alternator can give, so it takes what is needed from the battery. But with a discharged battery, the lamp is so bright with only the alternator. Strange.

The blinkers will flash at the right rate, but when revved, they just stay on, also a clear sign of the alternator raising the system voltage. I even removed the earth wire with the bike started, and the engine kept running with only the alternator juice, as well as the headlight gleaming.


So, it is either a matter of going back to the original lamp, or checking the harness in case there is some loose conector somewhere -which I doubt, because there are no one-way devices, if the battery powers the lamp, when the alternator gives its juice the current should flow back to the battery. I would hate to remove my H4 lamp, not only because it was hard to find a reflector, but also because I can't think of riding at night with a low-power headlight.


I have never had any trouble with H4 in my CB750, but it's true that its alternator is more powerful. Does anybody of you have H4 fitted in your CB350 or CL350?

[333]

I have one on my 350F.  I don't use it during the day.  Lucky for me the law allows for that where I live. 

[ohiocaferacer]

I've heard of the H4 bulbs causing problems with drained batteries in the CB350 twins before and that definately sounds like your issue.

Remember...the alternator is letting a charge goto the battery only over 2500 rpms. Even if I run with my stock headlight on during the daytime.....I have charging issues. So...running that big H4 bulb is definately gonna suck the juice. I agree the stock bulb isnt the best, but I really dont have much of a problem with it....unless i'm on a really dark county road....normal city driving is okay.

...and you are correct about the lighting coils on the stator.

As for the turn signals.....sounds like the 12 volt relay is tripping the signals at low rpm....but i'm guessing your voltage is dropping alot with the increased demand of the coils, which stops the blinking(combo of coils and H4 bulb). I would bet if you put the stock headlight in....the turn signal would work fine.......just a guess.

Hope that helps some,
Greg

[Raul CB750K1]

Quick update on this subject. After much searching I found a HS1 lamp, that looks pretty much like an H4 but with 35/35 watt, similar to the original lamp. Only one of the mounting tabs is bigger, so a little filing or cutting would be necessary to fit the lamp in the headlight.





So I remove the headlight, and when I remove the H4 I find something odd.... check the differences between this two H4 lamps...





It is rated..... 130/90 watt!!!!!!!! No wonder the battery drained!!!! What I can't remember is where did I get it from, I think it came in the headlight and I just used it straight away.


BUT, when checking the glow of the lamp, I could hardly tell the difference between that hi-power H4 or the regular H4. Anyway, the rating is clear, so I just installed a regular 60/55 H4 and will check if the battery drains or not. If it does, then it's time to try the HS1.



Will keep you updated.



Raul

[bryanj]

Yeh, I fitted some of those "Off Road Use Only" superwatts into a good old Fix Or Repair Daily Granada and had to put 4 relays in (one on each fillament) to stop the dip switch burning out!!

[tbpmusic]

Assuming it's a 350 with a "lights-off" position on the handlebar switch - in the headlight shell, find the white/yellow tube wite coming from the main harness.
Connect this wire to the yellow wire that also comes from the harness.
Now the bike will charge at its highest rate all the time, even with lights off.

This won't solve any charging problems, but will cause all three alternator coils to be working.
To find your charging problem shouldn't be too hard - many posts on many ng's deal with this issue.

bill lane

[mark]

According to my Honda manual, a "good" rectifier can have up to 40 ohms resistance. At what point does a rectifier stop being a rectifier and become a resistor? Does a 100 watt charging system really need a ballast resistor?



That solved some charging problems.


Happy trails.

[mystic_1]

Nice job on the rectifier, Mark.  Looks like a heatsink for Pentium processor?  I like how you handled the mounting bolt.


mystic_1

[mark]

Thanks mystic. It was either a pentium or k6 not that it matters. Ran a drill between the fins and it made a nice place for the stud from the old rectifier. Fits on the bike just like the real thing.

Buried it in goo and ready to go.


I hope a 35A 400V bridge can stand up to that powerhouse of an alternator.

[Bodi]

Selenium rectifiers (that old multi-plate thing) had some good points - they can take overload somewhat better than silicon (overloading causes overheating that raises the forward voltage and reduces the output; silicon just overheats and then dies - something like a Pentium vs a K6, actually) , and they have a lower than silicon (cool) forward voltage drop. But they also leak (reverse current) and have some odd behaviour after storage - they don't work well for the first while after not being used for a longish time. Your replacement bridge will be no problem at all. I like the waterproofing! There's no reason to use the old style unless you are a nitpicker about originality. My CB77 has a silicon bridge and - gasp - electronic ignition! ... sacriledge! But it charges as well as a CB77 can be expected to and the ignition has transformed the engine from a balky ankle killer when cold to a happy "electric starter" almost every time.