XS650SF - removal of light checker, RLU & Safety Relay

Mannyroad

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Hi All,

Ok, so I've acquired an XS650F (established through the patience and help from numerous members - thanks) that I need to get MOT'd before registering it in the UK. I've sorted most of the issues out with the bike, like getting the indicators/turn signals to work, fitting a front brake light switch, changing all the fluids and getting the brakes working properly etc., BUT, I'm having a hell of a job trying to figure out why the headlight won't power up, neither lo or hi beam circuits.

I've poured over the wiring diagram for my model and am hoping those who understand the electrics on this bike can clarify a few issues.

Fuse Box
This bike should have a fuse box. It doesn't. Instead, someone has removed it and it appears they've simply joined up corresponding colour coded wires, R to R, R/W to R/W, Br to Br etc. I think this was done by the import dealer/seller of the bike, trying to sort out electrical issues.. However, when I look at the wiring diagram it appears there aren't corresonding pairs of wires entering/leaving the fuse box (see attached clip of wiring diagram). Is the wiring diagram missing some of the wires, i.e. what do the R/W and R/Y wires connect to? I simply want to understand the original fuse box layout because I'm not sure if the botched wiring is connected up correctly.

Reserve Lighting Unit
I've read somewhere that to remove this I simply need to bridge the L/B & L/Y wires and ignore the rest. is this correct?

Light Checker
How can I disable this unit? Do I need to bridge any wires at the plug, like the L/Y wire which appears to be the feed wire for the lights from the Main Switch, or can it simply be unplugged?

Safety Relay
Again, can this be unplugged, or do I have to do any bridging of plug terminals? I read somewhere that this unit can be removed if one plans to 'kickstart only', but can it still be removed if I want to keep the electric start?

Headlight Issue
So, with Main Ignition Switch on, my headlight has no power, on either circuit. I can move back to the LH handlebar switch and:
1. check continuity between L/Y at handlebar switch and Y & G wires at headlight
2. if 1 above is ok, check if there's power at the L/Y (blue/yell) wire at Lights/Dimmer switch on handlebar, as I assume this is the incomming feed wire for the headlight, is this correct?
If no power at Lights/Dimmer switch, I presume I:
3. check continuity of L/Y wire between Lights/Dimmer switch and RLU plug. If good, check if there's incomming power at the L/B (blue/black) wire, would this be correct so far?
If there's no power at the L/B wire then I'm not sure where I should go from here. Looking at the wiring diagram it looks as though if I jump the L/Y wire at the Light Checker to the L/y at the RLU plug I should have constant power to the hi / lo headlight circuits.

Help would be much appreciated.

Note: When I got the bike (RLU, Checker & Safety relay in circuit) someone had stripped back the sheath on the L/Y & L/B wires to the RLU, joined these two wires together with a jumper wire and ran this jumper wire to the R/W wire running between the Safety relay and the Starter Switch. I'm not sure why but assume they were trying to find power for the headlight. I have actually removed the jumper wire and repaired the L/B & L/Y wires, so I'm back to the original wiring config.
 

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Jim

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Fuse Box
This bike should have a fuse box. It doesn't. Instead, someone has removed it and it appears they've simply joined up corresponding colour coded wires, R to R, R/W to R/W, Br to Br etc. I think this was done by the import dealer/seller of the bike, trying to sort out electrical issues.. However, when I look at the wiring diagram it appears there aren't corresonding pairs of wires entering/leaving the fuse box (see attached clip of wiring diagram). Is the wiring diagram missing some of the wires, i.e. what do the R/W and R/Y wires connect to? I simply want to understand the original fuse box layout because I'm not sure if the botched wiring is connected up correctly.
Power distribution.... fuse box.



1690412448005.png
 

Mannyroad

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Jim, that's fantastic. Thanks for the diagram. So, the wires that have been joined up by colour code are correct.
 

gggGary

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The headlight will NOT light unless the alternator is charging (motor running)
A 1979 XS650F only has one fuse, located under the RH side cover by the starter solenoid. A 1979 XS650SF has the 4 fuse block found under the seat.
40 years on who knows what changes to the wiring harness etc may have been done.
This 77 diagram is basically the same as the 79 F with the handle bar headlight switch having been deleted in 79.
77_XS650D.PNG

the Special and 2F model wiring diagram.
79_XS650SF&2F.PNG
 

Jim

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A 1979 XS650F only has one fuse, located under the RH side cover by the starter solenoid. A 1979 XS650SF has the 4 fuse block found under the seat.
Iirc, the previous discussion established it's a '79SF.... a Special.
 

Mannyroad

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The headlight will NOT light unless the alternator is charging (motor running)

That's interesting. I have no doubt that you're correct, I just don't understand why the alternator must be charging for the headlight to operate. Given the battery connects directly to the main switch, which in turn has the blue/yell wire running to the Light Checker, I presume it is this unit that is what stops it lighting unless the alternator is charging, no?

BTW, had to laugh. I've spent ages colouring in a b&w diagram so I understand it better. Where can I find the SF /2F colour diagram to download?
 

gggGary

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The alternator has a 4th wire (yellow), it feeds the starter cut off relay, that relay (seen on the LH side of this diagram) once activated by a functioning alternator also provides power to the lighting circuit, with the exception of the tail/brake light which is fed directly. Once on, that relay latches on, so failure of an alternator while riding won't plunge you into instant darkness. Instead the lights will gradually go dim.
While it's widely believed the starter relay is to stop you from starting a motor you haven't noticed is already running, ???? Yamaha states it was added to prevent starter run on when the motor fires.
late special lighting.jpg

The exact wiring may have changed a bit year to year, but it's all pretty similar.
 
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5twins

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So are you saying you have no fuses on the bike at all? That's not good, lol. I would add at least one, a 20A main fuse, on the red power line between the battery and ignition switch. You can add the missing 10A fuses later if you like, or not. I don't think they're absolutely necessary.

If you have the 7 wire light checker, which the wiring diagram indicates you do, you can't remove it without adding a jumper wire. Tail light power passes through it on the L/Y from the ignition switch to the L running back to the tail light. You must jumper those two wires together to get a working tail light again.
 

650Skull

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There is the thought by some the RLU has to be bypassed as it is an unnecessary component and it will let you down at some time so it isn't necessary.

If it is working i say keep it, not only does it automatically switch your headlight, low or high beam, (whatever one is being used), to the other high or low beam when riding if one of the Filaments blow it could ave you from a crash when or if you are riding at night. Or during the day if the filament blows again it automatically switches to the other beam. If you like the idea a headlight can help cars or other vehicles to see you during the day the the RLU will warn you if the headlight is having problems. The RLU is a safety feature and could save your life

I have put forward a few electrical links to help. I don't know where you knowledge is at so no offense intended if some of these seem third grade.
Some links to help with electrical.

Great write up by Xsleo on what happens when the key is turned on
https://www.xs650.com/threads/what-happens-when-you-turn-your-key-on.9625/

A good thread, Important. a lot of problems stem from poor grounds
https://www.xs650.com/threads/grounds-so-important.41775/

I made this up when i replaced my loom. I couldn't read a diagram, or relate the diagram to the bike. Found by doing individual circuits i got to know my loom and diagnose problems without having to run power through the bike.
https://www.xs650.com/threads/continuity-testing-made-easy.49917/

Good learning threads
http://www.ktm950.info/how/Electrical Shop/Wiring/Basics/Basic_wiring.html
https://www.xs650.com/threads/wiring-harness-musings.18925/

Great explanation by Jim on understanding how the charging system operates
https://www.xs650.com/threads/rewound-alternator-rotor.54276/

this is a good write up on replacing the factory Regulator and rectifier with an Automotive Regulator and bridge rectifier. Considered an upgrade due to reliability and a more even regulator output..................
NOTE; You have a B type charging system
https://www.xs650.com/threads/diy-reg-rec-5twins-and-jim.55842/
 
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Mannyroad

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The alternator has a 4th wire (yellow), it feeds the starter cut off relay, that relay (seen on the LH side of this diagram) once activated by a functioning alternator also provides power to the lighting circuit, with the exception of the tail/brake light which is fed directly. Once on, that relay latches on, so failure of an alternator while riding won't plunge you into instant darkness. Instead the lights will gradually go dim.
While it's widely believed the starter relay is to stop you from starting a motor you haven't noticed is already running, ???? Yamaha states it was added to prevent starter run on when the motor fires.
View attachment 247973
The exact wiring may have changed a bit year to year, but it's all pretty similar.

Wow, great bit of information there gggGary, thanks for that.
 

Mannyroad

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So are you saying you have no fuses on the bike at all? That's not good, lol. I would add at least one, a 20A main fuse, on the red power line between the battery and ignition switch. You can add the missing 10A fuses later if you like, or not. I don't think they're absolutely necessary.

If you have the 7 wire light checker, which the wiring diagram indicates you do, you can't remove it without adding a jumper wire. Tail light power passes through it on the L/Y from the ignition switch to the L running back to the tail light. You must jumper those two wires together to get a working tail light again.
Yeah, no fuses at all ATM. :) No intention of it staying that way, I fully appreciate the need for fuses.

I only really wanted to remove the RLU, Light Checker and Safety Relay because I wondered if they might be playing up and preventing headlight coming on. But the info gggGary has provided suggests I will need to run the engine to get a functioning headlight. I haven't got round to fuelling up and starting the engine yet, as I thought I'd try to sort the electrics first.
 

Mannyroad

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So, cheers everyone for the very helpful info. Now going to get the motor running, see if I have a headlight and, if so, get the bike off for an MOT. Keep you posted.
 

5twins

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Yes, the headlight only comes on after the engine is started and the alternator starts putting out a charge. A bit of that is sent on the yellow wire to the starter/headlight safety relay, triggering it, and that sends power to the headlight. That safety relay is actually two relays, one for the starter and one for the headlight. Headlight power comes from the headlight fuse on a R/Y wire and is fed into the headlight relay. Once the relay is triggered, that power flows out on the L/B wire to the RLU. From there, it is sent up to the hi/lo switch and on into the headlight itself.
 

Mannyroad

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Yes, the headlight only comes on after the engine is started and the alternator starts putting out a charge. A bit of that is sent on the yellow wire to the starter/headlight safety relay, triggering it, and that sends power to the headlight. That safety relay is actually two relays, one for the starter and one for the headlight. Headlight power comes from the headlight fuse on a R/Y wire and is fed into the headlight relay. Once the relay is triggered, that power flows out on the L/B wire to the RLU. From there, it is sent up to the hi/lo switch and on into the headlight itself.
Brilliant info 5twins. Thank you very much. It gives me a much better understanding of the headlight circuit. Been pissin around trying to figure the headlight out, rather than waste people's time on here, but that was clearly a mistake. Cheers again.
 
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