According to my parts book the OEM regulator part number is 74510-70a. Here's a link on eBay for one....
https://rover.ebay.com/rover/0/0/0?m...2F162042530800

 

I am having the same issues...I am running a Scorpion AGM sealed battery CCA380 28 amps/hr. The charging system is not charging the battery so I was considering direct replacement to stock 74510-70A. I have a 1971 FLH with a 96 Stroker 4 Plug Super B.

It was suggested that I convert to a 32 amp system and replace the stator, rotor, regulator...something like this but made in USA and better quality,

BUT after reading this thread, I am having second thoughts...job appears to be very involved just to get to the stator and somewhat difficult (for me anyway).

What would be recommended as a quality voltage regulator replacement to get my AGM battery charged up. Thanks.

 

Problem is the older charging system doesn't put out enough amperage for the newer AGM & Lio-Ion batteries, the old 17 & 22 amp regulators just don't kick out the umph they need to stay maintained. Been through this a number of times with my shovel buddies and I've been running the 32 amp systems since the 90's with no issues where the old 4 pin setup I'd lose a regulator every couple years. Yes it takes some work but it's worth it when done and any indy shop has a regulator on the shelf, no more hunting around and hoping .

I'm running a hi-po 93" shovel and she takes at least a 450CCA battery at the minimum to spin this thing and it still strains

 

early fxe were driven by the regulator the tach is AC not DC wiring a wire from the tack to the ignition Coil Will just ground out the coil and kill the motor if you change over to a modern alternator regulator you will also have to #change the ignition which doesn’t have a tach driver and also change the tach to a DC tach

 

If I switch to a DC tach, and the signal comes from the coil there shouldn't be an issue, correct?

 

just ran across this thread I have a 1975 fxe that i brought back to life after 15 years of sitting etc.... one of the WIP's Im dealing with is my tach and of course it is not working as my regulator has been replaced and it( according to my H-D dealer) drives the tach not the coil, been looking for a stock voltage regulator so I can put on bike and see of that solves problems....has anyone solved this dilemma yet, thank you

 

so if Im reading correctly all you do is run wire from tach to trigger side of coil... I also have 75 fxe.. thanks

 

I finally found a NOS AC tach for '74 and '75 FXE and it didn't work when I hooked it up. But the original tach took the signal from the voltage regulator, so still unresolved. I have a NOS DC tach that I intend to hook up to the coil but haven't yet, always seems to be something higher on life's priority list.

I ran across the following thread elsewhere and saved it for future reference. I don't recall the source:

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'74 and '75 FXE tachs get their signal from the alternator, the nature of which is a pulsed AC voltage.
'76 and later FXE tachs get their signal from the coil, which is a pulsed DC.
HD part#92040-74 is tach for '74 and '75, uses pulsed AC.
HD part#92040-76 is tach for '76 and later, uses pulsed DC.
HD part#74510-70A is regulator for '75 and earlier (has extra wire).
HD part#74510-75 is regulator for '76 and later (no extra wire).

I ran into this same problem about ten years ago when a friend bought a tach at a swap meet for his Sportster. When it didn't work, he gave it to me to trouble-shoot. Turned out to be one of those AC tachs. The only way I got it to work on the bench was to use a 12 volt filament transformer as a source and pulse it through a buzzing relay. Using a 12 volt DC power supply and the same buzz-box got me nothing. HOWEVER ---- Months after I returned it, the friend said he put it on his Sportster and wired it to the coil, and it was working. I didn't have any answer for this. Try it for a short test and see what happens; I don't think it will do damage. If it's not going to work, it will just sit there and stare back at you, in which case you will have to locate the correct regulator/rectifier or get a later model tach.

Good luck -- let me know how you make out.

Dennis A. Truxal

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thank you for the great info, yes my H-D dealer is telling me same thing basically, now when i go to eBay i see 74510-70A regs for sale there, they are aftermarket of course, just wondering if they will do the job or have that extra wire?? hoping i don't have to get a 76 tach, oh well...
again thx.