Hello All,

I am trying to figure out why my battery is not charging on my 1980 XS400. I have tested the alternator and rectifier according to the manuals specifications and everything seems okay. I am having some trouble testing the voltage regulator. According to the technician manual the regulator should be mechanical with some sort of adjusting screw somewhere on the body. My regulator does not seem to have an adjusting screw and I do not believe it is mechanical.

It looks like the part in this ebay auction:

http://compare.ebay.com/like/120578199689?ltyp=AllFixedPriceItemTypes&rvr_id=&crlp=1_263602_263632&UA=L*F%3F&GUID=831f21641280a0e205467ac6ff344981&itemid=120578199689&ff4=263602_263632

How do I test this unit? Can I follow the instructions in the manual and just ignore the part about the adjusting screw? If it is actually a semiconductor and not mechanical I do not believe it makes sense to measure resistance between different leads.

Also, the replacement I have found for the bike are quite expensive. I have a lot of experience in electronics and I was wondering if I can just make my own voltage regulator unit. Does anyone know the specificiations?

Thanks,

Adam

just read somwhere about voltage regs.

something about a certain type for certain alternators.

I'll have a mooch and see if me internet history comes up with something..

found this from chopper underground

The reg/rec doesn't know or care what brand bike it is on, all it's looking at is voltage.

You can use the reg/rec from a permanent magnet alternator but that's not an ideal setup. In that case you would hot wire the field so it is always on 100%. That is a major drain on the system [40 watts!] and will shorten the life of the already sketchy rotor.

try asking here

The better choice is one from an electro magnet alternator since it will modulate the current through the field to maintain voltage. There are only two types, ones that mount between the battery feed and the field [where the other leg of the field is grounded], and ones that mount between the field and ground [where the other leg of the field is fed a constant battery voltage]. The XS650 used both types. The early mechanical regulators were the first type, modulating the power. The later solid state bikes were the second type, modulating ground. You can wire either bike with any regulator so it doesn't really matter which you have now. If using a ground modulating regulator on an early bike you will have to insulate the brush screws since they ground out one of the brushes.

If you have an extra wire then it's likely a voltage sensing wire. For whatever reason, some bikes read the voltage after the ignition switch rather than directly off of the battery. Every one I've tested doesn't draw enough current to kill the battery so I'm not sure why they did it that way. Just hook this wire to the positive output that goes to the battery.

just read somwhere about voltage regs.

something about a certain type for certain alternators.

I'll have a mooch and see if me internet history comes up with something..

found this from chopper underground

The reg/rec doesn't know or care what brand bike it is on, all it's looking at is voltage.

You can use the reg/rec from a permanent magnet alternator but that's not an ideal setup. In that case you would hot wire the field so it is always on 100%. That is a major drain on the system [40 watts!] and will shorten the life of the already sketchy rotor.

try asking here

The better choice is one from an electro magnet alternator since it will modulate the current through the field to maintain voltage. There are only two types, ones that mount between the battery feed and the field [where the other leg of the field is grounded], and ones that mount between the field and ground [where the other leg of the field is fed a constant battery voltage]. The XS650 used both types. The early mechanical regulators were the first type, modulating the power. The later solid state bikes were the second type, modulating ground. You can wire either bike with any regulator so it doesn't really matter which you have now. If using a ground modulating regulator on an early bike you will have to insulate the brush screws since they ground out one of the brushes.

If you have an extra wire then it's likely a voltage sensing wire. For whatever reason, some bikes read the voltage after the ignition switch rather than directly off of the battery. Every one I've tested doesn't draw enough current to kill the battery so I'm not sure why they did it that way. Just hook this wire to the positive output that goes to the battery.

Thanks for the quick response. Regarding my other questions:

Why does the manual state the regulator is mechanical? Is it possible I am missing the screw?

Adam

Thanks for the quick response. Regarding my other questions:

Why does the manual state the regulator is mechanical? Is it possible I am missing the screw?

Adam

Adam, I think you do have a screw loose

the mechanical one might have been replaced in the past with an electronic one. newtronic did a combined reg/rectifier as a direct replacment, but they are now a defunct company!