Topic: keep engine running or headlight on.....need help

[jaguar]

my 74 cb125s started spuddering last night while riding it home.  headlight started getting dim then shut the bike off.   if i turned the headlight out all was well and then i could turn the headlight back on for a little bit before the whole thing happened again.  what do you think it is?  the battery in new a few months ago and was holding a charge.

[333]

Have you checked the fluid in the battery?

[mlinder]

Even the 160's don't have enough of a charging system to run for any real length of time with the headlight on.
I'm sure the 125 is as bad, if not worse, than the 160's.

[jaguar]

fluid is good.  i charged the battery just to see if that helps

really honda made a bike that you cant run that long at night?

[Klark Kent]

34 years of corrosion will rob the electrics of their zazz.  if you clean up the contacts I would expect better performance.  the corrosion can be traslucent and the only way to know for sure is to clean everything, but start with the fuse contacts and clean everything that has to do with the headlamp circuit and see what happens.
good luck

[KB02]

Also, double check your charging system, as well. Make sure that it is actually putting out enough juice for the job.

[bradweingartner]

You can also save a ton of wattage by converting to LED lights everywhere on the bike.

[Klark Kent]

acually it sounds like you have an overwatted headlight- i think honda used 35W headlight bulbs, but a lot of the readily available replacements are 50W.  it should be written on the side of the bulb.

good luck

[333]

My guess is the bike is stock.  Not many light bulb alternatives for 6 volt bikes.  My suggestion is to clean EVERY CONNECTION on the bike that you can get to.  I can't remember, can you even turn the headlight off?  My '80 didn't have a switch, and it seems to me that was around the time('75ish) that they stopped giving you that option.  The other suggestion I would make is to not always shift into the highest gear.  If you're just tooling around town(what else would you be doing on a 125?) , use a lower gear and keep the revs up.  A lot of these old bikes don't charge until they get up over 2k.

[Bodi]

As I recall the bike has a two output alternator which adds power when the headlight is switched on. It's not unusual for the headlight switch to go bad so that the headlight comes on but the extra juice doesn't get connected. The various bullet connectors in the wiring are the most common problem, with wires broken in the harness where they flex around the steering stem the next most common trouble after 30+ years. The actual alternator coils are usually fine. I've had rotors demagnetized after many years too, but '74 should be fine (the "rare earth" magnet material was still used, after about 76 this got too expensive and less excellent magnets were used and most bikes went to induced field (no permanent magnet) systems).

[mazingerzeca]

34 years of corrosion will rob the electrics of their zazz.  if you clean up the contacts I would expect better performance.  the corrosion can be traslucent and the only way to know for sure is to clean everything, but start with the fuse contacts and clean everything that has to do with the headlamp circuit and see what happens.
good luck

How should these connections be cleaned? Coca Cola?

[andy750]

Check my recent thread on my CB750K4 bike dying under similar conditions to yours -mine turned out to be the battery. If you check in the FAQ - Electrics section, Bodi and others have written some great info for how to check the charging system - it helped me a great deal!

Good luck
Andy

[333]

How should these connections be cleaned? Coca Cola?

Never.  Pepsi all the way.

Seriously, there are several contact cleaners.  Honda markets one.  Use a long bristle brush to get into the nooks and crannies before it evaporates.

Now I want an english muffin.