Regulator / Rectifier - Lithium & Lead Acid - Honda CB350F CB400F CB500 CB550 CB750

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Battery not charging? Might be time to replace your rectifier or regulator, and why not replace them both at once with a part that will work better than the originals. This Rectifier / Regulator Combo will replace both your old rectifier and regulator. Unlike many other units, this regulator rectifier is designed to work with lead acid based batteries, including Gel batteries as well as lithium batteries. You must have a fully charged battery in perfect working order before installing a new regulator rectifier.

Dimensions: 82mm Long x 30mm tall x 80mm wide
Mounting Hole spacing - 66mm (measured center to center)

Replaces these Honda OEM part numbers: Rectifier: 31700-333-008 Regulator: 31400-300-035

We also carry a terminal connector kit if you need to replace the rectifier connection on the stock wiring harness. If the stock connector is brittle and the terminals are corroded, it's best to replace it.

Here's a very helpful SOHC forum thread on testing the charging system 

Note: The white 5 wire connector plugs into the stock wiring harness, replacing the old rectifier. The 3 male spade connectors plug in where the old regulator connected. Corroded / loose / damaged wiring is a very common cause for charging system issues, make sure all connections are clean and secure. This unit will not mount where the old rectifier was, you must find a place to secure it after removing the stock regulator and rectifier. The body of the unit does not need to be grounded.

Fits Honda:

CB350F - 1972-1974 
CB400F Super Sport - 1975-1977
CB500K - 1971-1973 (1971 needs female terminal and spade connectors replaced)
CB550F Super Sport - 1975-1977
CB550K - 1974-1978 
CB750F Super Sport - 1975-1978
CB750K - 1969-1978

Designed to work with 3 phase charging systems on pre-1979 Honda SOHC4's

Will also work on the CB750A Hondamatic 76-78 but the plastic plug must be removed and swapped for an 8-pin version

10 Reviews Hide Reviews Show Reviews

  • 5

    Posted by Elmer on 29th Aug 2021

    I have a Restoration shop in the Philippines and been a customer of 4into for years so far i never any problems with all the items i bought from them and im very satisfied with their prices and most of all their customer service. Been a loyal customer ever since.

  • 5
    Great way to upgrade.

    Posted by Hans on 14th Aug 2021

    I have been having charging problems since the day I bought my 1975 CB550 about 20 years ago. So many things upgraded and still had charging issues. Realized that my regulator rectifier was probably old and swapped it out with this one. It’s a wonderful and easy way to upgrade your electrical without having to rewire your wiring harness. Relatively inexpensive and as simple as plugging in and bolting on.

  • 5
    Never should have bought from amazon 1st

    Posted by Kris B. on 15th Apr 2021

    I made the mistake of buying the cheap one on amazon. It drained my battery... This one is rock solid 13V and reports great through my munit blue. '78 Honda CB750k brat

  • 5
    Great replacement

    Posted by Richard on 3rd Jan 2019

    Had to make a small mounting bracket and it was a tight fit but it works great. Replaces rectifier and regulator. Much more stable charging voltage.

  • 5
    simple replacement. perfect result.

    Posted by Tim on 10th Dec 2018

    Unplug the old stuff. Plug in the new thing. Check it. Hey, works great! Go for a ride.

  • 5
    Great product!

    Posted by Matt on 6th Oct 2018

    Fits my 76 Honda CB 550 and works great! Thank you!

  • 5
    Low cost alternative

    Posted by David Altman on 14th Aug 2018

    I have about 200 miles on my rebuilt cb550 with no issues. We'll see if it holds up over the long term but so far, so good. I have no reason to believe it won't.

  • 5
    Problem solved

    Posted by Unknown on 15th Jul 2018

    Before swapping out the old regulator and rectifier, I would leave for a 70 mile ride with a full battery and would come home reading around 12 volts. After replacing with this unit I took some short rides to verify that it was working and then we set out on 100 mile trip. Made it home and the battery was fully charged. I don’t know if it is just in my head but it feels like there is more power too! Thank you 4 into 1! (This was on a 78 cb550k)

  • 5
    Excellent upgrade

    Posted by Mike W. on 22nd Aug 2017

    Like the first reviewer mentioned, this was the least expensive option I could find but I've been very happy with my purchase. It works great on my CB350F and the wiring was plug and play. I'm now using a maintenance free AGM battery. This bike starts easier than it ever has. Highly recommend!! Thanks 4into1!