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Discussion Starter · #1 ·
Hi Everyone,

I have a 1973 CB350G that I've (luckily) had relatively few issues with in my 2 years of ownership. I bought a new Yuasa battery for it the first spring that I owned it, and it's been great.

However, recently, I've had issues with the bike starting (usually starts first kick). I rode it downtown recently and it refused to start for me, stranding the bike. Luckily it was in a place that I could leave it, and so I popped the battery out and got a ride home from a friend where I hooked the battery up to my trickle charger. At this point, I figured that since I hadn't ridden the bike much in the previous month or two, it must have just died and needed a good charge.

Fast forward to that night and I bring the fully charged battery back to the bike and pop it back in. The bike starts with a vengeance on the first kick. Like, easiest kickstart of my entire ownership. I'm excited and start to take a back way home. About 15-20 minutes into the ride, the high beam flickers and dies, and the engine follows suit about 5-10 seconds later.

It was a long push home to get the bike to my garage, where it's been sitting the last couple of weeks. Out of frustration and being busy, I haven't bothered touching it.

Any ideas? A friend mentioned it might be the alternator, and a similar thread online mentioned something about the rectifier. I'd love to get it sorted out soon, and I'm praying it's something I can do in my garage to avoid having it towed to a shop.

Any ideas would be much appreciated!
 

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It could certainly be the battery or the charging system, but since it's a Yuasa battery (assuming you've kept the cells full) it should last a couple years or longer... so my guess is the charging system. Does it still have the original rectifier and regulator on it, or does it have a modern combo unit on it?
 

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Discussion Starter · #3 ·
I'm pretty sure the battery is fine since it's still relatively new and I've monitored the cells pretty closely while I've had it. Everything else on the bike is original as far as I know (previous owner hadn't ridden it in ~30 years before he got it running and sold it to me). Safe to assume the rectifier and regulator are from 1973.
 

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I'm having a similar issue as well. I'm new to all this and picked up a '72 CL350. I figured I would just replace the battery anyway for an AGM, however, upon hooking it up the rectifier started smoking!!!

I immediately disconnected the new battery and have been apprehensive about doing any electrical work until I understand it for the most part. Perhaps it started smoking because the battery is more powerful? The exact battery I have is MotoBatt MB12U (12V 15 Amp) 160CCA Factory Activated QuadFlex AGM Battery

I'm worried it might not be as simple as installing a new regulator/rectifier combo as the guy who had the bike hacked up some of the electrical system (bypassed the killswitch and for some reason there's two terminals connecting to the positive post of the battery.)

But anyway, for OP, I think you're on with the rectifier being suspect as its main responsibility is recharging the battery.
 

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I can with pretty much 100% confidence say your problem has nothing to do with the AMP/Hr Capacity of your new battery.

A battery will ONLY output what is demanded from it.
If you connect it to a circuit that require .5 Amps it will push .5 Amps to the circuit.
If you connect it to a 6 Amp circuit it will push 6 Amps thru the circuit and so on...

If you connect it to a dead short it will push the MAX it can thru the path available.
If there is a fuse along that path you will typically blow the fuse as it overloads.
If there is no fuse you will most likley melt the insulation off the wires in the circuit.

I suspect either your rectifier is shorted (VERY COMMON if it is still an OEM RED with THIN Square Metal seperators)
Or - you connected it wrong.

Do you have a wiring diagrahm ?
It might not help much if the PO really hacked up the harness, but it might help you track things back.

Attached is a Hi-Res Graphics of the 350 basic wiring diagrahm.
Right - CLICK and OPEN in a NEW Tab Use the (+) to expand a zoom in on the circuits.
You can also to a SAVE-AS to a USB and have it printed in large format by an office supply store like FEX-Office or Staples.

Wiring_cb350_stock_wiring.jpg
 
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Hey thanks for your reply on this. I definitely plan on snagging a new regulator/rectifier combo.

I was going to grab the one from Common Motor Collective. I really feel like I didn't make such a noob mistake hooking it up incorrectly but now I'm starting to second guess myself.

Also thanks for the colored wiring diagram. I've got the factory service manual but the colors on this one are so much easier to follow.

EDIT: Well judging by the way the terminals were screwed onto the new battery and the orientation of the positive and negative cables coming from the bike, there's a decent probability that I hooked up the battery backwards. Wow, what an idiot.

The question now is how much damage did I do? It was hooked up for maybe 7 - 8 seconds.

20181011_124705.jpg
20180912_180946.jpg
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As if I don't seem dumb enough I can't figure out why the picture is being uploaded upside-down or how to rotate it.

Anyway, for what it's worth, I think I do remember throwing in the old battery and the headlight was still dimly lit. Research points me to looking for a main blown fuse.
 

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Yes it looks like your new battery has the Pos & Neg in reversed locations from the OEM.

I suspect you are going to find it very hard to stretch the OEM cable to the correct terminals.

You might get lucky on the damage.

The 350 has ONLY (1) Fuse Located in a holder that snaps into a clip in the top front of the battery box.

It is a METRIC FUSE.
An SAE Fuse will NOT work correctly.
AN SAE Fuse will have a larger but only slightly larger diameter to the end contacts.
It will cause the contact surfaces NOT to make full contact and WILL overheat.
The typical end result is the fuse holder is destroyed.

Any Honda or Jap bike dealer will carry the correct 15 amp fuse.

Or - Cut out the fuse holder and replace it with a modern BLADE Type.

Either way will work.
BUT... do NOT just put in an SAE and expect to go for a nice ride,you will find yourself broke down some place.
 
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I have the common motor one, but never got around to installing it since things are working well. Perhaps this winter.
 

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Awesome, solid advice on the fuses. Thankfully the battery has 4 locations where you can install the terminal brackets.


I must've been so excited when I got it in the mail I screwed them on without any consideration for the orientation of the terminals on the bike.
Here's to hoping it works. I'm sure I'll be back if it doesn't.
 

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Yes it looks like your new battery has the Pos & Neg in reversed locations from the OEM.

I suspect you are going to find it very hard to stretch the OEM cable to the correct terminals.
Those Motobatts have two terminals for each of positive and negative, so you just attach the cables as before, having unbolted and moved the terminal connections on either side.
 
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