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68 CB450 AGM and rectifier

Bender01

New Member
Joined
Jan 6, 2023
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Location
Bluffton SC USA
So I have a 68 CB450. It is bone stock but I want a better battery. I purchased an AGM MB12U. Upon further searching it has been said I need a better rectifier to handle it or it will fry it.
I purchased the Sparck moto product rectifier as it said plug and go for most Honda twins.
Well i got the old one out and started to look for the plug and mine is bullet connectors. I really don't want to cut this new rectifier and try to make my own connections.
Has anyone used the AGM battery in a stock system without a problem?
Thanks
Ben
 
The stock charging system will produce too high a voltage for that battery.
One of the DOHC folks will be along to advise on how to do this since I know very little about this model.
You can contact Matt, owner of SparckMoto/Vintage Connections, for advice also. He's a member here as Sonreir https://www.vintagehondatwins.com/forums/member.php?41-Sonreir
 
I'd go with contacting SparckMoto; they may even have harness adapters. You will need a few more connections for it to work.
 
I’ve put the Sparck Moto reg/rec on both a ‘67 Bomber and my ‘69 K2 450. I can try and take some photos of my install today. I can’t remember exactly how I did it right now.
 
Bender01,
After looking at both of my bikes and what I had done then also re-reading your post I need some clarification from you. Did you buy just a rectifier from Sparck Moto or did you get the regulator/rectifier combination unit from them?

The reason I ask is you mention bullet connectors but your stock rectifier (located by the battery) should have a rectangular plastic plug with 4 wires and blade terminals. The 4 wire colors should be pink, yellow, green, and red with a white stripe.
Your bike, if it is a USA K1 450 version (looked like it to me), should also have a voltage regulator (located under the battery box and air crossover tube). The regulator does have 3 bullet connectors with colors black, green, and yellow. It seems you may be confusing these connections with those of the rectifier?

Depending on whether you bought only a rectifier or the rectifier/regulator combo would dictate how you approach the wiring on this swap.

Maybe a current photo of the wiring around your battery and rectifier would help see exactly what you have.
 
^^^Good observation Chris, the mention of bullet connectors threw me off as well but you're right, the OEM regulator has them while the OEM rectifier does not.

For the OP, this is what he actually needs from Sparck Moto (if it is not what he bought/received). Sparck Moto owner Matt (also VHT member Sonreir) knows these bikes so I'd be surprised if it was the wrong component.

http://www.sparckmoto.com/Products/Detail/7
 
^^^Good observation Chris, the mention of bullet connectors threw me off as well but you're right, the OEM regulator has them while the OEM rectifier does not.

For the OP, this is what he actually needs from Sparck Moto (if it is not what he bought/received). Sparck Moto owner Matt (also VHT member Sonreir) knows these bikes so I'd be surprised if it was the wrong component.

http://www.sparckmoto.com/Products/Detail/7

It looks like Sparck Moto only sells the combo unit now so that is probably what the OP has. If that is the case, here are some simple instructions for connecting the combo unit that Matt had posted elsewhere in the past and I had saved:

Step 1: Remove old rectifier
Step 2: Secure new unit in place
Step 3: Wire it up. Going from the harness to the new unit, the following colors should match up:
Yellow to Yellow
Brown to Pink
Red to Red
Step 4: Ground the green wire from the unit to bare metal on the bike
Step 5: Tie the black wire from the unit into a black or black/white wire in the bike (flasher relay, starter solenoid, and rear brake switch all have the necessary wire)
Step 6 (optional): Disconnect the pink and yellow wires from the lighting switch and on the harness side of the connection, plug them into one another to enable full charging even when the lights are off
 
Yes i have the combo. The unit doesn't look like the rectifier at all so I went to the regulator. It would bolt in there I think.
Ill look better at the rectifier tomorrow. There is a plug that looked right but the size was so different.
I dont want to cut anything if I dont have too.
Wont this affect the stock regulator?
I may be able to put the AGM in my 550 if it can handle it.
Thanks
 
Yes i have the combo. The unit doesn't look like the rectifier at all so I went to the regulator. It would bolt in there I think.
Ill look better at the rectifier tomorrow. There is a plug that looked right but the size was so different.
I dont want to cut anything if I dont have too.
Wont this affect the stock regulator?
I may be able to put the AGM in my 550 if it can handle it.
Thanks

If you bought the right AGM, it will be fine in the 450 when you use the Sparck Moto combo unit. The OEM regulator can be removed because what you bought is a combination unit, both rectifier AND regulator in one. Any product we recommend here is because we've used it and know it works properly.
 
The old regulator does need to be removed and the wires taped off? Or just leave the old regulator in place?
Thanks
 
You don't HAVE to remove it, but why leave it there? It will never be used again. And Honda was smart about their wiring design, any wires that would be "hot" when the key is on would be in female connectors so you wouldn't have to tape anything.
 
WinterSol: You were thinking correctly, the Bomber (65-67) did not have a regulator. The regulator started on the 450 with the ‘68 K1 model. To confuse things a bit, the ‘68 general export K1 450 did not have a regulator however.

Bender01: The new combo looks like it should bolt up where the old regulator was but the holes are a bit too wide on the new unit for it to work. You have to elongate each hole an 1/8” or so with a file or a mill to make it fit there. If I remember correctly the wire harness and plug from the old rectifier will reach to connect to the new unit if mounted in this location. Also there is the bullet connector for the black wire that is available for use from the old regulator connection if mounted here.

I mounted mine in the location of the old rectifier on my K2 450.
E8AC7323-E334-4195-8344-4B458352BBE6.jpg
I made a small bracket out of 1” c-channel that I could bolt the new combo unit to and then used another bolt to connect to the bottom mount for the original rectifier. I also had to add a double bullet connector to attach the black wire to but you could always make a jumper wire to run back to the available empty boot from the regulator.
E8AC7323-E334-4195-8344-4B458352BBE6.jpg
The last thing to remember if you mount your new unit in the original rectifier location is to plug the two holes in the air crossover tube that were for the regulator with 6mm bolts so you do not get unfiltered air sucking in.
 
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