Topic: Dim headlight brightens when revved, and a dead battery.

[zach9865]

Hi everybody!  I'm a noob here, which is probably obvious after reading the subject of my question.  I have a '77 Honda CB550F that I recently bought.  The PO said that it probably needed a new battery, so I went ahead and bought one.  Charged it up and I was ready to ride I thought.  So I cruised around for a while and while parking, noticed that the headlight was pretty dim at idle but brightened up considerably when I revved the engine.  I rode for another few miles in the next day or two not thinking much of it.  I went to start it up a day or two later and no juice.  No starter motor, no headlight, couldn't kickstart, no electrical power.  I'm pretty sure it's a problem in the charging sequence, but am unsure about where.  Reg/rectifier?  Does the headlight brightening when I rev it rule anything out?  Any help would be appreciated.  Thanks a lot!

[NickC]

Charge your battery, take voltage at battery
Start bike, take voltage at battery.

Let's see what you got from there 

[Nikkisixx]

Hi and welcome!  It might not mean anything that your light gets brighter at revs.  The system works better at  around 2500rpm, so this might indicate the system is working.

I hate to answer your question with a question but do you have a tester of some kind to troubleshoot your electrics?  Something like this:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?itemnumber=90899  
You may well need it to track down electrical gremlins.  

[zach9865]

Thanks guys!  Yes I do have a voltmeter like the one you linked to, but I can't find it for now so I used one that doesn't have decimals until I find the other one.  Voltage at the battery w/o the engine running is at 12v and w/ the engine running it stays at 12 until I rev past, as you said, 2500 rpm, and then voltage goes up to 13v.  Seems like it should be charging.  Maybe I'm just idling to much and going on short trips that run it down?

[CB650 Wolf]

I had the same problem with my 650. Had about the same readings and symptoms with the headlight/neutral light. It ended up being the rotor.

[MCRider]

I'm not near as good electrically as some guys here. But... if the headlight gets brighter and dimmer with revs, usually means its charging, which means the reg/rect, are probably OK.

Once I had a short in the starter button and it would drain the battery ovrnight. Took me forever to figure it out. I could charge up the battery and it would run all day. But it would go dead overnight.

Crack open your handlebar switches and look for bare wires.

I'm suspicious you have a small short, bare wire somewhere.

[campbmic]

Well it sounds like its charging to me. It could have just been a fluke/you left the key on?

Ride your bike around for 20 minutes then pull it into the garage and shut everything off. Take the reading at the battery. Wait a few hours then take the reading again. If it is draining then you have a problem.

[MickeyX]

Try this... it should help you figure out if something isn't working right or you have a short somewhere. Good luck.  It works for our bikes and many other manufacturers as well. It's easy to follow.

http://www.electrosport.com/technical-resources/library/diagnosis/pdf/fault-finding-diagram.pdf

[Nikkisixx]

Maybe I'm just idling to much and going on short trips that run it down?

Yes, it can.  When driving stoplight to stoplight, with a lot of engine starts, running lights and turnsignals, you will smack the battery.  As you'v seen, it won't make charging voltage until it sees some revs. 

[cameron]

I have struggled with this same problem for years, it seems.

My solution was: when I was only riding short trips, to set my idle adjuster to 3000.
It is annoying, but it ensures that I get a decent charge out of the thing.

Also, I only kickstart. I haven't used my electric for 5 years, I bet... because I don't trust it not to just totally drain my battery.

But as MCRider said.. MY problems all started with a short.. in a side lamp.

[MCRider]

As I've said, electrical systems are not my strong suit. But I do know that there is no reason why we would have to baby these bikes in normal usage. Tens of thousands, hundreds of thousands were made and ridden with no care for how fast the idle speed was, or how much stop and go traffic we were in or whether we used the electric starter or not.

So you may need to baby it to get thru a troubled period. But once its sorted out, not a care should be given to keeping a battery charged for the life of a battery, until its ready to die from old age.

PS: I will qualify that by saying that letting them sit dormant for long periods as we often do, as they are not our everyday rides, will work against us. But in general, with regular normal use, keeping the battery charged from within is a non-issue.

[bistromath]

Your charging system is likely OK. They were never great on the 550 to begin with, and they don't improve with age. Things you can do to improve battery life:

* Polish the bullet connectors all over your wiring harness with emery cloth, and reassemble with dielectric grease. Even just unplugging and replugging can have a huge effect on contact resistance.
* Polish the spring clips in the fuse box with emery cloth and squeeze the clips together with the fuse removed to add more spring tension.
* Look to see if the PO has mounted a 55/65W headlight instead of the stock 35W headlight. The stock headlight was so dim as to be dangerous, but the charging system could keep up with it. Several people (including me) have mounted the DDM 35 watt HID kit (it's under 40 bucks) with excellent results.
* Look to see if the PO has mounted 3 ohm coils instead of the stock 5 ohm coils. 3 ohm coils use 20 watts more power.
* Last but not least, if you're riding for short trips or in the city most of the time, keep your battery on a battery tender. Get a good one, as the cheap ones seem to destroy batteries after some time. I mounted a female cigarette lighter adapter to my battery, and a male plug to my battery tender. The female end on the bike tucks behind the sidecover when not in use, and makes it easy to plug the bike in when it's in the garage. This also lets me charge my phone on long trips.

As a final comment, given the alternator setup on these bikes, if you spend most of your time in stop-and-go traffic or idling, there is no way for the battery to charge no matter WHAT condition the charging system is in. They do not charge at idle like a car does, so every stoplight drains the battery. A charging system in good shape on the 550 will start to "break even" around 2200RPM. Idling at 3000RPM is not recommended because it can cause the engine to overheat in short order. Use a battery tender on a city bike.

[number13]

I had the exact same situation on my 500,
it turned out that the main rectifier feed wire (red on my bike)
had corroded to the point that there was maybe only
a strand or two in contact. I had to remove the electrical
panel to diagnose/fix it,  but once
inside it was very obvious, so if all else fails look there.

[zach9865]

Thanks a lot guys,  a ton of useful info there.  I interestingly enough haven't had an issue the past few starts after trickle charging the battery for a while.  Maybe too many short trips and stop and go idling killed me.  I am gonna meticulously go through the electrical system this weekend and clean, polish, and dielectric grease as many connections as I can find.  Thanks for all the help.  I'll update if the problem persists!

[cameron]

New info as of today.

So, for the last 5 years, my story was similar to you'all.. poor charging, poor starting.. whatever.

Anyway, Yesterday I put in one of those Scorpion AGM's . . and it is a god-loving new bike. My horn works all the sudden. the electric start actually turned over.. (it hasn't done that in a year). Kicked to life on the second kick this morning. The turn signals are 25 bpm faster... and I have full power all the way up.
It even finds neutral easier. Don't ask me how that is related.. but it is true.

The one I took out was a standard NAPA that I just put in in November.. .and tested out just fine. sat at 12.5V.
Everything is stock right now except I have a Dyna ignition.

http://www.batterystuff.com/batteries/motorcycle/sYT12C.html

I couldn't recommend it more. Today, she ran better than ever. Seriously. Since the day we first met in that poor old fella's barn, may he rest in peace, she has never been as smooth and peppy. That extra Volt really means a lot, I guess.

[gane]

Zack, As posted, Your charging system will typically cause H/L to get brighter after @ 2 grand.. ' tis the nature of the beast" , a dying  new battery is not.. I'd try this.. disconnect one or the other of your' battery leads and connect a test light/ light bulb in series between batt. post & it's wire.  Key off. any sign of lum's indicates key off draw. There should be none. if there is, remove fuses til light goes out. if still present with all fuses out, unplug reg/rect. (one blown diode can allow a "marginal charging system" yet drain batt, whist setting) if light goes out when pulling fuses, consult wiring diagram for bits in circuit & dicconect  til light goes out. hope this helps. G

[loudsky]

All of these posts have been helpful so far. I haven't started to try and figure out the problem yet... I've just been keeping two batteries charged. I feel like I have a better idea of how to go about trying to figure out the problem now. Thank you all. My bike is a 1978 CB750 k and I love it with the cafe bars on.