Sure seems correct.. is that the original rectifier?
Sneezles61

Yep, that's the original rectifier.

Manual description is backwards.  Diagram shows "normal" connection...  positive hooked to Red, negative to White.  But that's when the diode needs to block the flow of power or the battery would backfeed into the stator coils.  Not good.

With positive hooked to white at rectifier, then the "positive" power from stator can get through rectifier and put juice in battery.   Clear as mud?

Ohm readings are meaningless unless you are using the analog meter as Yamaha intended.  Some digital meters can't even be used to test a diode with the ohms function.. 

The diode test function shows voltage drop when power is flowing through rectifier...  generally between 0.2 and 0.8 volts depending on diode type and meter.

Bottom line- it's fine. 

P.S. I've seen meters that have "reverse" voltage output in ohm mode...  With RECTIFIER DISCONNECTED AT WHITE WIRE one easy test is Battery plus to red side of rectifier.  No voltage should be at white wire.  Then connect white rectifier white to battery red MAKING SURE RED RECTIFIER WIRE IS NOT GROUNDED OR CONNECTED TO ANYTHING BUT VOLTMETER.  You should get near battery voltage at rectifier red.  CAUTION! with Battery positive connected to white, if you short the red to ground you will smoke the rectifier in a split second.  I've made that mistake. 

I usually use a AA dry cell for this test with rectifier off the bike.  Much safer than using the Yamaha battery which has enough amps to destroy the rectifier real quick.  And in fact I only do this with a test light...  If I have my meter I don't use the battery. 

Rectifier is basically just a one way valve. 

 

I just pulled the fuse back out to measure it, to order some new ones, and noticed it's an odd size. It's about a quarter inch by just a little bit under an inch long. Most that I have and see online are either longer or shorter; and smaller in diameter.

Do most people just put a more modern inline blade fuse holder in? I've got several hanging around, and I think that's what I might do.

mark your an enduro genius 

tom - I tormented myself with this rectifier things too until I blew cash on a new one and it had the same readings of 0 and ~.5x ohms and realized it’s the measurement.  the Yamaha fuses are a bit shorter than the busse fuses we used to crawl under the dash to replace in the 70s!   I like to keep original so I pay the extra bucks to get Yamaha type but any fuse of proper amperage should work. 

I don't unless harness is butchered.  Original type holder is still readily available from Yamaha.  Fuses are not too uncommon and can be found cheap too...  harder to find locally now that electronics supplies like Radio Shack and Fry's are disappearing.  6mm x 25mm. 

Yamaha, Honda, and others used them as well as a lot of electronics.  DrATV has them for $0.99 ea.  dratv.com/fuoldstgl1or.html

Mikesxs has 5 for $2.09  www.mikesxs.net/yamaha-xs650-25mm-glass-fuse-10amp-pk-5.html  Lots of other places too I'm sure. 



 

Thanks MarkT, I just ordered some from Beatrice.