Topic: CB350 Four Charging issues

[dougan]

Okay, first real hurdle to cross with my new '72 CB350 Four.

Took it out for its first ride.  Ran it 7 miles without the headlight on (by accident) and it worked fine.  Turned the headlight on and shortly after, the battery died, and the bike wouldn't kick start.  Threw it on the charger for 20 minutes and it started up just fine.

This is the trend.  It'll start up and run but if the headlight's on it will quickly die, along with the battery.  And I'm talking dead dead, like no neutral indicator working.

Before I get too far, I did find this thread: http://forums.sohc4.net/index.php?topic=105888.0 Pretty similar, I just wanted to run my issues by you guys without threadjacking.

I hooked up my multimeter across the terminals.  I can see that the alternator is charging the battery somewhat-- but maybe only 12.5-13 volts when I rev up to 4,000 or so.  Obviously ain't right..  It seems like the majority of the wiring is stock, and I couldn't find any grounds that looked bad (haven't looked hard enough to be positive yet).

Sounds like the next step would normally be to open up the casing for the alternator, but it looks like the bike was put down at some point and these screws got a bit mangled-- probably won't want to come out with just a regular bit.  I have a set of screw extractor bits if push comes to shove. I just figured I'd ask you guys about it before I go down that road. Can you think of anything else I should be looking at before I go down that road?

The bike's basically a tease now; it runs so well but I can't ride it legally without the headlight.

[HondaMan]

I have a '72, too! And I'm SO jealous that yours runs....     

First thing to check: the headlight. If it is a halogen bulb of more than 40 watts, get one of the 35/35w halogen bulbs for it, or get a Honda Stanley 35/35w lamp instead. These Baby Fours don't make much candlepower! It was about 3 years ago that some German outfit started offering these 35/35w H4-sized bulbs, a real lifesaver for us. I found mine at a local "generic" (i.e., not a brand bike) bike shop.

Next: make sure the taillight bulb is a genuine Honda Stanley bulb. Reason: many, if not most, of the made-in-China #1157 and even #1034 bulbs today are drawing as much as 200% of the specified current for the bulbs. Both cars and bikes are suffering from this: in cars with plastic reflectors, the hotter filaments are melting the taillight!

Last, but not least: make sure the Green ground wire for the harness has a clean connetion where it meets the frame, and the alternator connectors must be clean. Even a little corrosion can really impact these little alternators. Once you get these little things sorted, it will be reliable as ever, again! 

[dougan]

I looked at the headlight yesterday, I could have sworn it said 25/35, but maybe it was 35/35 and I read it wrong.  Either way, not 40w or more.  Haven't looked at the taillight yet.  I don't think the taillight is the problem though because I turned the key off in the wrong direction by accident, which made the taillight light up for about an hour, and the battery was still not dead when I noticed it that way in my garage.

I'm really thinking it's going to be inside that alternator casing, I just don't know how the hell I'm going to get in there.

[hoodellyhoo]

I wouldn't be digging into the alternator casing just yet. You could remove the sprocket cover to gain access to the alternator plug. You can check the resistance on the stator coil windings and for continuity in the field coil. If you haven't already, download a shop manual for the bike. The procedure for checking these things is in there.

[vames]

Did you or the PO ever try and jump start the bike with jumper cables? Hook them up with crossed polarity even for a second? One or more of the diodes in your rectifier could be screwed (which would make it charge a teensy bit but not nearly enough). Get yourself a digital multimeter and a manual (or find directions on this site) and 1) check the rectifier 2) check the field coil and stator (you don't need to open up to do this - you can do it from the plug). Clean all of the connections along the way. You'll probably find out what's wrong.

[dougan]

I wouldn't be digging into the alternator casing just yet. You could remove the sprocket cover to gain access to the alternator plug. You can check the resistance on the stator coil windings and for continuity in the field coil. If you haven't already, download a shop manual for the bike. The procedure for checking these things is in there.

Cool, I will open up the sprocket cover and look in there-- I guess I just kind of assumed everything would be under the alternator cover.

Did you or the PO ever try and jump start the bike with jumper cables? Hook them up with crossed polarity even for a second? One or more of the diodes in your rectifier could be screwed (which would make it charge a teensy bit but not nearly enough). Get yourself a digital multimeter and a manual (or find directions on this site) and 1) check the rectifier 2) check the field coil and stator (you don't need to open up to do this - you can do it from the plug). Clean all of the connections along the way. You'll probably find out what's wrong.

Unfortunately don't have a lot of info about the PO.  I'll take a look at the rectifier.

Thanks for all the tips.  I think I panicked a little.  I'll look at these areas and see if I can find the problem.

[flybox1]

yes, you can easily adjust the rectifier to charge your battery properly.  did it on my '72 350F and it was easy.
but first, you need to go through and service all your connections and your fuse block.  shine them up real good and treat with dielectric grease.
be sure your grounds are good and clean as well and do the things listed above.
retest your battery and the voltage at idle, 2500 and 4000 rpm.
only then, adjust  your rectifier.

[Bodi]

there's nothing much to go wrong in the alternator case, but it just unscrews. The coils are attached to the cover. You need the side cover off to get enough wire slack to get the assembly off though. Don't undo the three screws in the middle of the cover, they hold the field coil on.
there is a set of bullet connectors under that side cover, the three yellow wires and the field coil wires have them. These cause much grief, maybe because they're already hot in there. these should be cleaned and tightened at the least, and a bit of dielectric grease is a good idea on reconnection. If the plastic sleeve is burnt looking you should eliminate the bullets by soldering the wire joints and insulating with two or more layers of heat shrink tube. Once overheated the metal in the connector sockets permanently loses its "spring".

[dougan]

OK, crossing my fingers, but I think I got it working right.

I re-did all the grounds and all of the connections, except for the ones inside the headlight casing, and checked, no change.

Moved to the rectifier.  Stock-type rectifier--this thing gets pretty hot, I can see why people swap these out for modern ones.  What was odd was that it was not attached using the connectors shown in the shop manual, but soldered to the other wires (pretty shoddy job, too).  So it's definitely been messed with.  The grime on the connections tells me it wasn't too recent, though.  Did the ohmmeter tests recommended by the shop manual, and they indicated that the rectifier was fine.  So I rigged up bullet connectors to connect it back to the electrical system.  Fired up the bike and everything was magically working more like I'd expect.  12.5 v at idle, about 14 at 4,000 rpm.  I only have an analog multimeter, so that's not exact, but definitely better than maxing out around 12.5.  It was dark by the time I finished, and I'm not used to riding yet, so I didn't ride it around to see if it would die yet.  But I'm thinking it might be fixed.  Must have just been those connections.

Thanks for all the help, everyone.  You guys rock.

[hoodellyhoo]

Sounds like you got it fixed. Good job!

[HondaMan]

OK, crossing my fingers, but I think I got it working right.

I re-did all the grounds and all of the connections, except for the ones inside the headlight casing, and checked, no change.

Moved to the rectifier.  Stock-type rectifier--this thing gets pretty hot, I can see why people swap these out for modern ones.  What was odd was that it was not attached using the connectors shown in the shop manual, but soldered to the other wires (pretty shoddy job, too).  So it's definitely been messed with.  The grime on the connections tells me it wasn't too recent, though.  Did the ohmmeter tests recommended by the shop manual, and they indicated that the rectifier was fine.  So I rigged up bullet connectors to connect it back to the electrical system.  Fired up the bike and everything was magically working more like I'd expect.  12.5 v at idle, about 14 at 4,000 rpm.  I only have an analog multimeter, so that's not exact, but definitely better than maxing out around 12.5.  It was dark by the time I finished, and I'm not used to riding yet, so I didn't ride it around to see if it would die yet.  But I'm thinking it might be fixed.  Must have just been those connections.

Thanks for all the help, everyone.  You guys rock.

Hmm...if it gets hot, that usually indicates they are leaking (electrically). It might just be time for a new one? It only takes one jump from a 10 amp or bigger charger (or a running car) to toast one. The new ones from Honda are better, with a higher PIV rating so that doesn't happen anymore.