Topic: Is this a charging issue?

[apetersonboy]

I was riding my bike home when about a mile into the trip the bike started to run rough. It refused to rev any higher than it was at, (my guess is about 2k, I have no tach.) and was missing pretty bad on one cylinder. By the time I got home it was even worse. As soon as I let off the throttle to coast to a stop it died. There was no electrical power to anything. My speedometer back light was lighting up, not even a click from the starter solenoid. The battery was completely dead.
I took the battery out and noticed that the acid levels weren't quite what they should be. Some too high and most too low. Could this have caused the loss in power? Any help is appreciated.

[Markcb750]

The liquid levels being a little high or low should not mater, unless they were allowed to go dry at some point, or filled with water that was not distilled.


Check your connections and charging voltage.

[bjbuchanan]

First thing that comes to mind is what is your cruising rpm? If you tried to rev up to 2k when it ran like crap you cruise too low. 3500 and up, otherwise you are constantly depleting the battery. Our charging systems only put out around 1/3 watts of full output at idle.

The answer is sorta, but doesn't sound like something actually wrong with the bike but the riding style. Don't take offense

[TwoTired]

I wonder what bike he has?

Anyway, you don't get spark without battery power, particularly at idle.

Have the battery tested and the charge restored if still good.

The measure the battery voltage vs RPM of the alternator to see if the bike has charging issues.

[Vinhead1957]

How old is the battery?  You get 3 yrs normally.  Charge it normally after fill and then load test it.

[apetersonboy]

The battery has maybe 4 or 5 miles on it. Brand new! Also I just evened out the levels of acid tonight and charged it. Put it back in the bike and still no power.
Found a blown 15amp fuse. Replaced that and the bike behaved fine. Didn't start or ride it, but everything seemed to be back to normal. Except when I flipped the high beam on it blew that fuse so I'm pretty sure it was just the wrong size fuse. It was just one I found laying around.

When I get a new fuse tomorrow I'll test the voltage when the bike it at idle and also see if it surges when I rev it.

[Vinhead1957]

It should not blow a 15 amp fuse.  Look before leap. 

[TwoTired]

It should not blow a 15 amp fuse.  Look before leap.

I agree.  But, they can "blow" from over current, or be melted by external heat sources.
They are designed to blow from the heat generated from within by too much heating from the current it passes.  This assumes a stable ambient temperature value.  However, if the fuse clips develop resistive connections, the heat generated from that can derate the fuse to an effective lower value.  Like 10 amps or less.

Since we don't know which model bike he has or if the headlight still has the stock wattage rating, further speculation is rather pointless without needed information.

[Vinhead1957]

Way too technical ! No headlight should draw over 15 amps..  I do agree with corroded connections could be part of the problem

[apetersonboy]

It should not blow a 15 amp fuse.  Look before leap.

I agree.  But, they can "blow" from over current, or be melted by external heat sources.
They are designed to blow from the heat generated from within by too much heating from the current it passes.  This assumes a stable ambient temperature value.  However, if the fuse clips develop resistive connections, the heat generated from that can derate the fuse to an effective lower value.  Like 10 amps or less.

Since we don't know which model bike he has or if the headlight still has the stock wattage rating, further speculation is rather pointless without needed information.

My bike is a 1978 CB 750f ss. The bumb is a H4 bulb, when I bought it, I was under the impression that it is indeed what stock was.

[TwoTired]

No headlight should draw over 15 amps..

That's not the point.  A 15 amp fuse can melt without any current flowing through it, just by providing an external heat source.
Try it!  Just put your soldering iron on one of the end caps.  The internal link will melt.

The H4 is not stock and they are available in different watt ratings.  Probably should find out what it's marked.  Still, see if you can hold your thumb on the main fuse while the bike is operating without blistering.  Rev the motor to raise the line voltage.

[Duke McDukiedook]

No, stock is a sealed beam light, not an H4 bulb.
You need to run through your connections and wire check to make sure everything is tidy and not corroded or frayed, that includes the fuse connections.

[apetersonboy]

I inspected every block connector in the battery box area. Cleaned every single one to shine and used electrical connection cleaner. I plugged it all back in, turn my key to on, and the main fuse turned red inside and melted. Same exact thing as before.
I unplugged all of the connections to see if that would make a difference; it didn't. So, does this point to all of the connections that reside in the headlight bucket?

[TwoTired]

Does the main fuse survive if you remove the headlight fuse?

A direct short should pop the fuse immediately.  If you can watch it go red before melting (I've never seen that on a 15 amp fuse), then you are drawing slightly more than the fuse can handle.

You'll have to start isolating circuit branches to figure which one is sucking more power than planned.  Assuming the fuse clips are making a good low resistance contact with the proper size and shape fuse.

[apetersonboy]

Made some progress, I disconnected everything again and then plugged the right hand controls.
Pulled the brake lever and the fuse lot up red and broke.


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[apetersonboy]

So I'm gonna inspect the right hand control internals for an exposed wire and if I don't find anything I'll inspect the brake light circuit.


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