Charging system: rectifier?

[sartoriusrock]

I have a 1982 xs650 heritage special with a bad charging system. I am getting 12.5 volts with the bike running off a fully-charged battery, but the voltage does not increase at all when I rev it up. After consulting with the previous owner and my grandfather who knows more about electrical than myself, I believe/hope this may be a result of a bad rectifier. As far as diagnosis, how much ac volts should be going into the rectifier? When checking the white wires to ground at the regulator/rectifier clip I am 7.8 volt dc between the white wires and ground. Is this too low/does this indicate a bad rectifier? Layman's terms, please, I'm a mechanic, not an electrician.

Thanks!

Dan S.

 

[xjwmx]

The best way to attack this is with what's known here as curly's charging guide. Google it to find the text. It's pretty methodical and postpones the shooting in the dark for a few days Picking the rectifier already is shooting in the dark too soon....

Also, I think the H supplement to the manual, or a letter or two earlier, has a charging troubleshooting guide for the Specials. http://www.biker.net/650parts_index.htmlhttp://www.biker.net

 

[XSLeo]

You check the ac voltage by probing from the white wires to the other whites not ground. Test the three as three sets of two.
Should get above 10 vac. If you bypass the reg then it should read as much as 20 vac.
On your 83 the reg and rec are a combined unit. If the reg or rec goes bad you put on a different one. Or a new one.
Before you start buying and swapping the proper testing should be done so you buy and swap the right parts.
Up at the top of the page is an XS650 tech button, push it. Scroll down the list and you will find a link to Curly's guide. Links to reg/rec replacements too.
Leo

 

[sartoriusrock]

Thanks for recommending Curly's Guide. After a simple removal of the alternator cover, I realized that I was getting very little resistance from the brush contact points on the rotor (while I should've been getting 5.0-5.7 volts I was getting 1.3). My dad has had a worn out rotor kill the charging of multiple bikes of his, so this seems like a likely culprit. A new rotor is on the way! Hopefully we have the problem solved, but if not, I will revisit this page.

Thanks for all your help!