Pre recommissioning electrical checks?

Its been a long time

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Making progress with the 77 XS650D I have acquired. Latest foray is into the alternator. Good news is there's no visible oil leaks from the crank seal, clutch pushrod seal or sprocket seal. Quite surprised at that. Front sprocket, nut and tab look fairly recent as does the chain and rear sprocket. However, alternator checks -

I haven't put a battery near the bike yet. I want to be pretty certain the wiring doesn't burst into flames or something before I put a fully charged battery near the bike. I'm not at all confident with electrical items so I've started by checking the alternator out first. The alternator rotor looks recent and the brushes are in very good condition, about 4mm worn. I believe the rotor to have been changed long enough to wear the brushes by the 4mm. The resistance across the copper brush tracks is 5 to 6 ohms falling, no short circuits. I have polished the brush tracks and have new brushes to install.

The alternator stator, looks original 47 years old. It's obviously mucky but not oily or corroded. I put a meter across the three white wires in the outlet harness plug and there's no shorts to earth. There's about 1 ohm between each pair of the three white wires. I don't really know what I'm doing here but with no shorts and consistent readings between the three white wires, it's good to go? I'm not going to attempt to clean the stator windings but might use a paint brush to brush off the worst of the dirt.

I think I'm OK to go to the next step of checking out the rectifier and regulator on the bike now. They are clearly 47 years old. I haven't done this before, so I'm off to see what I can find here about rectifier and regulator checks before I do anything more.

Pictures attached.

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Today's progress. Alternator stator reinstalled with new brushes.

Voltage regulator removed and opened up. It's original Yamaha/Hitachi and I would say is pretty recently fitted NOS. It's far too clean be anything else. See picture below. Opened up to check the two contacts gaps and it's pristine, zero sign of any arcing and the two gaps bang in the middle of the specified range. Planning on just reinstalling it.

Checked ignition coils primary resistance, 4.4 to 4.8ohms, both coils being similar. So I'm calling those good.

Rectifier - I'm less sure about this but it's partly my inexperience in testing electrical items that isn't helping. I think the item is Yamaha but it is old. I guess it's used from a breakers yard as it has the telltale paint marker markings on it. Typical of used parts in my experience. Testing according to the manual red to 3x white, black to 3x white. There's no reverse current flow, the diodes look OK in that respect. But where the ohm meter readings should be in single digits, I get about 180ohms. Consistent when testing all three white to black and red, testing in one direction only. So, I don't know conclusively that the rectifier is OK or not. Anybody have advice on that? Thanks.

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Your components sound OK but the true test will be firing up the bike and checking the charging output. If it's a little high or low, a small adjustment of the regulator may be needed.

On most of the stators I've tested, the readings on the three white wires didn't match the book values exactly, but the stators worked fine. I think the important thing is that the readings are all the same and match.
 
Your components sound OK but the true test will be firing up the bike and checking the charging output. If it's a little high or low, a small adjustment of the regulator may be needed.

On most of the stators I've tested, the readings on the three white wires didn't match the book values exactly, but the stators worked fine. I think the important thing is that the readings are all the same and match.
Thanks that would be my take as well. I am sure the rotor, stator, regulator are all good. My inexperience has me doubting the rectifier. But getting the same reading across the three rectifier phases reassures me enough to say it's OK to start.

I have just found a possible issue with a fuse in a red wire, that's correct according to the book for a 77 XS650D. But there's an obvious home made connection into a wire adjacent to the starter relay. The blue home made crimp connection. It doesn't look right and it's exactly the kind of thing I am looking for before putting a fully charged battery on the bike. What do you make of it from the picture below? Thanks.

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If you want to test the rectifier ..which are rather robust one must measure forward and backward direction
Manuals there
https://thexscafedotcom.wordpress.com/2011/01/10/xs650-manuals/

When you power on / up be sure to have fuses of the right size or smaller installed
There is the risk it shorts somewhere when getting hot.

Not sure if for your Year model but something like that.

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That may be OK. Normally, the fuse connects to a red wire that branches off the end of the battery cable. If that wire is missing, the fuse could be connected to that large terminal on the starter relay instead.

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If you want to test the rectifier ..which are rather robust one must measure forward and backward direction
Manuals there
https://thexscafedotcom.wordpress.com/2011/01/10/xs650-manuals/

When you power on / up be sure to have fuses of the right size or smaller installed
There is the risk it shorts somewhere when getting hot.

Not sure if for your Year model but something like that.

View attachment 258995
Thanks. Yes, I did that. The manual gives a low ohms resistance reading but mine is quite a bit higher. However, it's the same for all the tests and it's consistent no current flow in the opposite direction. So I'm happy to say it's testing OK. Of course, putting power on it is something else. But it looks OK to do so.
 
That may be OK. Normally, the fuse connects to a red wire that branches off the end of the battery cable. If that wire is missing, the fuse could be connected to that large terminal on the starter relay instead.

View attachment 258997
Ah, gotcha. I'll take a closer look in the morning. I don't like the look of those pre insulated crimps. That's going to come off. I might put a ring terminal on there attached to the relay live terminal. That'll get rid of that home brew crimp. Thanks again.
 
Yes, that's the main power feed into the bike harness that powers everything. Best the connections are good.

Many of us upgrade the regulator to an automotive one and the rectifier to one from the electronics world. A rectifier is a rectifier is a rectifier, they all do the same thing (convert AC to DC). There's no need to buy an expensive motorcycle specific one, a much cheaper unit from the electronics world works just fine. Here's a thread that outlines the upgrades .....

https://www.xs650.com/threads/diy-reg-rec-5twins-and-jim.55842/
 
Yes, that's the main power feed into the bike harness that powers everything. Best the connections are good.

Many of us upgrade the regulator to an automotive one and the rectifier to one from the electronics world. A rectifier is a rectifier is a rectifier, they all do the same thing (convert AC to DC). There's no need to buy an expensive motorcycle specific one, a much cheaper unit from the electronics world works just fine. Here's a thread that outlines the upgrades .....

https://www.xs650.com/threads/diy-reg-rec-5twins-and-jim.55842/
I've seen here the recommendations for rectifiers and regulators. For sure, first hint of a problem and I'll swap out the rectifier. I would prefer the original if it works. All the ones I see on Google are made of Chinesium and probably 1 per cent of the quality of those originally used. All the best.

Edited to add - it doesn't look impossible to open up the Yamaha rectifier and solder new diodes in there. I have no idea if anyone has ever done that though.
 
If you want to stick with Yamaha stuff, some XS400s and XS500s of this era used a more modern style (totally enclosed) rectifier. All you need do is change the plug from the female type to a male type .....

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I once tried to repair a XS 650 rectifier
First find a Diode and then remove the old one and get it in .
I gave up.

Have used automotive rectifiers and other after that they are quite robust.
I go for higher specs that can take more of a beating . Probably the part with least problems
If I were you I would have one Electronic regulator at home stand by . Not expensive and does a better job regulating
 
I once tried to repair a XS 650 rectifier
First find a Diode and then remove the old one and get it in .
I gave up.

Have used automotive rectifiers and other after that they are quite robust.
I go for higher specs that can take more of a beating . Probably the part with least problems
If I were you I would have one Electronic regulator at home stand by . Not expensive and does a better job regulating
Thanks for information about a Yamaha rectifier repair. I've just been googling around. Yes, I think it's perhaps a good plan to buy a standard 3 phase bridge rectifier and keep it as a spare.
 
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