What does a selenium rectifier do?

[Newpaltzwonder]

This is probably the wrong place to post, but here it goes...

The other day, I bought a 1974 Honda 250/360 twin motorcycle.
It doesn't run yet...the timing is off and only only cyclinder has a spark. I'm trying to get the starter to work so I don't have to keep kick starting it...

My question is, what does the Selenium Rectifier do? I traced the starter lines to it and it looks worn out. If I knew what it does, this might help me get the starter going.

Any help would be great!
Thanks,
Newpaltzwonder


I think this is it, I'm not sure. The battery is connected to it.

[Duo]

Okay, a selenium rectifier is simply a diode whose semiconductor material is selenium, where, usually today, they are made with silicon or germanium. Selenium rectifiers often fail after 20 or so years of service and you can replace them with silicon diode rectifiers. You'll need to replace it with one that will handle enough current though. Perhaps find a Honda dealer that would have a new part for it, or try to find someone who can figure out how to rewire it for a silicon diode.

[Newpaltzwonder]

Thank you!

Newpaltzwonder

[Duo]

You're very welcome.

[Circlotron]

Originally posted by Newpaltzwonder
My question is, what does the Selenium Rectifier do? The battery is connected to it.

99% sure it is a half wave rectifier for the alternator. Outboards sometimes have a similar setup.

[Duo]

Yes, that is most likely what it is. The combination of the alternator, rectifier, and battery makes a nice little DC power plant. If your rectifier is bad, your battery won't charge and you'll basically have no output from the alternator into the system.

[Newpaltzwonder]

Ok, it turns out that the rectifier is ok. I posted the wrong picture, that is a selenoid...oops. Well the selenoid is bad. It is gunked up and the wires are broken. Hence, that is why the starter is not working.(I hope).
Does anyone know where I can get a replacement or something I can substitute? If not, it's ok, I'll keep searching.

Thanks,
Newpaltzwonder

[nobody special]

I would think that your Honda dealer could help you out. If not, try this place:

THE RICE PADDY - 1450 North Grant Avenue - Columbus, OH 43201
Phone: 614 297-1404 Fax: 614 297-6930

They specialize in old japanese bikes.
You will find that the charging system on your 250/350/360 twins is generally pretty weak. Many people keep them on a trickle charger when they're not being ridden. Replacing the selenium rectifier with silicon diodes is a tricky subject, because of the much higher resistance of the selenium. You could possible (probably) run into problems with too much voltage when using a regular diode.

Steve
'95 ST1100
'73 CB350 Twin
'71 CB350 Twin