1981 XS400: Charging issues / low power

[Hayahisa]

I'm a new owner of 1981 xs400 and I believe I am having issues with the charging system. When I first got this bike, it ran ok but dies and goes low power when the battery runs out. It'd be very likely that the previous owner has replaced the alternator as I saw a trace of it. I checked resistance on the old anlternator and it had no connectivity. I swapped that alternator with another one that I had from the other engine. The running voltage was unstable around 14.9V with 2000-3000rpm. With the old alternator the voltage never changed after the engine started. I swapped the regulator as well and now the running voltage is 12.3-12.4V whereas the charged battery itself is 12.6-12.7V. I just went for a test run and for some reason it started losing power while going up on a steep hill. At this point I have no idea what to do. I'm swapping around with old parts, so now I'm thinking of swapping the separate rectifier and regulator to two-in-one rectifier regulator I've seen on Mike's xs. Does anyone have any idea what's going with this bike? Thank you in advance.

 

[tstidham]

Seems the alternator putting out the 14.9 is what you want and replace the regulator to limit it to 13.8-14.2. I used a transpo c8313 (I think that's the part number) from and old 80's dodge pickup with the slant six. If you also get the regulator pigtail, it's a pretty easy swap.

 

[Hayahisa]

Seems the alternator putting out the 14.9 is what you want and replace the regulator to limit it to 13.8-14.2. I used a transpo c8313 (I think that's the part number) from and old 80's dodge pickup with the slant six. If you also get the regulator pigtail, it's a pretty easy swap.

Ok perfect Thank you for the recommendations.