1981 XJ 550 rectifier/stator questions

My son recently purchased a 1981 XJ 550. It has sat for the better part of 20 years. Has 8600 miles on it and it has seen a few previous owners. I'm not familiar with these bikes but we have been plugging away at getting this back to life. At this point we have the motor running and the clutch and braking systems all working. Are issue is the stator/ alternator doesn't seem to be charging the system. I'm not 100% sure how or were to test this and or the rectifier. The battery is brand new (3weeks) and was trickle charged at 2amps. Not sure if the headlight/blinkers are connected to this but the headlight and blinkers don't work either. I have replaced the weak fuse holders in all 4 circuits and was going to check relays in morning. Any help and or advice is greatly appreciated.

 

Check voltage at the battery terminlas with the engine running. You should see at least 13.8 V at 2,000 RPM.

 

Battery was fully charger two days ago and I probably started bike at least dozen times since. I checked voltage at terminals and got 11.47-11.9 regardless of rpm. idle thru 5000 no change. After that I also disconnected the red wire coming from bike to battery on starter relay and bike died. Bike did same when I disconnected positive on battery as well.

 

[
note the caution about removing wire
there are brushes in the alternator that may need to be changed they have waer indicators on them.

tests for both

full wiring diagram link
http://frankjohansson.com/stuff/xj550/XJ550ElectricalDiagram.html

 

+1

The alternator cover is on the left side of the engine, directly behind the cylinder bank. The brushes are on the inside of the cover and have wear marks engraved in them (wear limit is 10mm). The alternator slip ring may need to be cleaned as well (use a hard eraser to clean the copper on the slip ring).

 

This is what I find under the cover. Brushes look like they are still good, marks are easily seen. Not sure about the surface of the rotor. Is there a way to test the voltage coming out of this thing?

 

Voltage output was checked when you checked the voltage across the battery, which indicated no charge.

From there you need to isolate to the defective component to rotor, brushes, stator, Rect/Reg or wiring. If you have the service manual it provides a fairly comprehensive check of each component. XJ550H provided the applicable pages from the manual.

One other common fault other than the brushes is corrosion and even melted connectors on the stator harness connector to the main harness. You can identify the stator connector as 3 pins with all white wires located under the seat. It will need to be disconnected to ohm the stator per the isolation procedure.

Try to go through the procedure, and ask more questions if you get stuck along the way. While you have the AC Generator cover off go ahead and check the rotor resistance across the slip rings for the 4.5 ohms +/-10%

 

I don't have a manual. My son plans on keeping this so we are gonna need to get one. The connectors all look ok, minor cleaning needed. I have an ohm meter and just tested rotor resistance with my meter set 200 and I got 5.0, I tested the stator (3white wires) disconnected and got 1.1-1.0 in every possible configuration.

 

click on the photos i posted has the instructions for testing alternator and rectifier see caution about removing battery wire while running

 

down load manual $9.95 its for a seca but works for you
https://www.tradebit.com/filedetail.php/100227614-download-yamaha-xj550-xj-550-1981-81

or you can pay $21.95 for 81-81 xj550
https://www.tradebit.com/filedetail.php/274376933-yamaha-xj-550-1981-1983-online-service-repair
both are downloads

 

I just saw them, too late for the caution note gonna have to deal with it. I put it back together and got the following. 7.3 between the brown and green 1.1-1.0 between white wires in all configurations.

 

I have the xj550 manual pdf, when I get home from work I can try to send you the link to download. Unless you want the book.
-EM

 

One other thing that needs attention is the clip on the master link of the chain is backwards!

 

As in the master link effects voltage??

 

As in the master link coming off when riding can allow the chain to come free and bust the engine cases, which rapidly drains the oil, which seizes the engine, which then can't make any voltage....so yes. Note that that entire scenario is unlikely, but I have seen it happen, and it is far more likely on a dirtbike than on a roadbike. The chain looks like it needs to be replaced anyway.

 

No but if that clip comes off and throes the chain voltage will be your lest of your worries.

 

K moe types faster than me.

 

Mater link and chain are all good.

 

when testing the regulator v2 with key on is 12.8 volts v1 is also 12.8 with motor running it actually drops at v1 to 12.20-12.17

 

The V1 and V2 readings in the service manual are reversed. V2 at the brown wire is battery voltage, and at a minimum will be battery voltage but should increase with engine RPM. V1 at the green wire should start low (bike not running) at 1.8 or less, and slowly climb when RPM is increased. . So, if the green wire is at approximately 12V with the bike not running, that indicates that the Rect/Reg cannot sink current through the rotor, and is likely defective. Only other issue that would cause that is if the ground to the Rect/Reg was missing.

It is easier just to forget V1 and V2 and just think green and brown - brown being supply and green being control.

 

This is the rectifier/reg, someone has obviously been in it b4 us. there is one orange wire on this unit that is not connected but Im not even sure its the correct part.

 

I can tell you right now that it isn't an OEM rectifier.
-EM

 

hopefully someone knew what they were doing when they rigged that up........

 

Using the correct parts makes many problems magically disappear........

 

You are so learned

 

Well I just located a guy in upstate NY that had a bunch of parts he wanted gone. Pile has 2 original rectifier/regulators with mounting bracket and ignitor in it so Im gonna hope for a simple plug n go

 

Wasn't me..... Who did you find?

 

Some guy in Cairo/Cobleskill area. His father wanted it out of his garage

 

Quite a bit south east of me.... Wonder who it is

 

seemed like a regular Joe

 

Just an update for all. I replaced the rec/reg and it works great. I also installed the headlight relay that apparently was missing and now that works. Thanks for all the great advice, very much appreciated!

Carl