safety relay yellow wire

[furrygreg]

My son & I are finishing the wiring on his 1978 Yamaha XS650SE project bike. As part of the build up, we installed a new Boyer Brandson electronic ignition to do away with the old stuff, and a new PMA alternator kit to get rid of the old alternator. We got both kits from Mike's XS. I liked the idea of getting everything we needed in two complete kits, and the installs went well by following the kit installation instructions and viewing posts on this site. We have only run into one problem. What do we do with the yellow wire that runs from the safety relay that used to plug into the old alternator? From what I understand, it would use any voltage above 2.5 volts to open the circuit to the starter relay to keep the starter from being engaged while the eneing is running, and it also closes the relay to send power to the headlight. I saw this system in action before we tore down the bike, so I understand how it works. I like the idea of the bike automatically cutting out the starter while the engine is running as this is my son's first bike, and it will be one less thing for him to worry about. If we want to keep this system operational, where should I run the safety relay yellow wire to for a good power source? If we are not able to use the safety relay anymore, what is the correct way to rewire the harness to delete the safety relay. I suspect we are not the only folks that have been baffled about this subject. We appreciate any help we can get with this.

 

[Grinder]

I suppose you could run a 12V power source via some kind of switch to the yellow wire to activate the relays. This would give you a off/on switch for the headlight which wouldn't be a bad thing. I'm not sure if the relays would handle 14+ volts as they usually don't see than many volts. The starter cutout wouldn't work as it originally did but it would keep you from accidently activating the starter. Maybe the electrical guru's have some better ideas.

 

[5twins]

Not sure about the starter part but the headlight relay can be bypassed or eliminated by simply unplugging the blue/black wire to it. Then your handlebar on/off headlight switch will function normally all the time .....

 

[Grinder]

My bad, I thought 77 was the last year for the bar lights on/off switch.

 

[furrygreg]

Thanks for the help I have received with this so far. I contacted Mike's XS about this since I bought the PMA from them. They say that I can hook up the yellow wire to any one of the three yellow wires that come out of the alternator by splicing it in. I am considering whether I want to do that or just bypass the safety relay altogether. My 91 FLSTC doesn't have a safety relay, & it has never been an issue over the 21 years I have owned and ridden it.

 

[5twins]

I like the idea of the starter safety relay, I don't like the headlight one. By simply unplugging that one wire, the headlight relay is taken out of the picture (still functions but it's not connected to the headlight any more) but the starter relay still does it's thing.

 

[XSLeo]

On your FLSTC the starter engages a gear on the clutch basket, the clutch basket is linked to the engine trjrough the primary chain.
On the XS650 the starter engages a set of gears that spin a cross shaft that in turn spins another set of gears that spin the gears that engage the engine. The safety relay protects all these gears and the cross shaft.
From what I have read the way Mike's said to wire the safety relay to one of the yellow wires from the stator works to trip the safety relay.
Will going with out the protection of the safety relay cause premature failure of the gears? My guess is not real soon but eventually.
If you plan on keeping the bike for long I might use the safety relay, if you sell it soon, then don't. The problems won't show up till the next guy has the bike.
Leo

 

[rebel542]

Tie it into one of the yellow wires coming from the stator and be done with it.

 

[rebel542]

I did it and it works fine.

 

[Grinder]

Just curious, if tying the yellow to one of the 3 stator wires works, why did Yamaha bother to add the 4th wire from the stator to do the job? I think you only get about 8 or so volts from the factory setup on that wire.

 

[rebel542]

I have no idea why Yamaha engineers did that. I only know I've rode mine many miles tied into a stator wire with no issues. Hope this helps.

 

[mrriggs]

Just curious, if tying the yellow to one of the 3 stator wires works, why did Yamaha bother to add the 4th wire from the stator to do the job? I think you only get about 8 or so volts from the factory setup on that wire.

Yamaha did do it that way on the Virago (no fourth wire). That is where the idea came from to do it on the PMA conversion.

 

[furrygreg]

I just wanted to say thanks to all of you that responded to my question about the safety relay yellow wire. We are going to splice it to one of the wires coming off of the new PMA alternator. I may or may not bypass the headlight. This bike has the lights on & off switch that should work if the headlight is not wired in to the safety relay. It would be good to be able to shut off the lights to start the bike if the battery is going bad. I did the same thing to my 91 FLSTC by clipping off the jumper wire on my ignition switch.

 

[aldo5468]

I just wanted to say thanks to all of you that responded to my question about the safety relay yellow wire. We are going to splice it to one of the wires coming off of the new PMA alternator. I may or may not bypass the headlight. This bike has the lights on & off switch that should work if the headlight is not wired in to the safety relay. It would be good to be able to shut off the lights to start the bike if the battery is going bad. I did the same thing to my 91 FLSTC by clipping off the jumper wire on my ignition switch.

I agree with what you say. Just would add that IMHO, whether it's done automatically by a relay or manually by a headlight switch, it's good to have the headlight off when energizing the starter regardless of battery condition, to maximize the voltage available to the starter. This should maximize cranking speed and minimize time for engine to start. Having said that, if my bike died in the middle of an intersection where I'm waiting to turn left across opposing traffic, I don't think I'd worry about taking time to turn off the headlight.

 

[XSLeo]

If you hook the yellow wire from the stator to the yellow of the safety relay the headlight won't come on till after the engine starts, on the bikes that have the safety relay control the lights.
So if your lighting circuits work right just hook the yellow up and be happy.
Leo

 

[johnno3au]

If you hook the yellow wire from the stator to the yellow of the safety relay the headlight won't come on till after the engine starts, on the bikes that have the safety relay control the lights.
So if your lighting circuits work right just hook the yellow up and be happy.
Leo

Do you think this may fix my starter overrun problem after installing a pma?

 

[retiredgentleman]

Do you think this may fix my starter overrun problem after installing a pma?

Yes, it should unless the starter gears/springs are hanging up.

 

[johnno3au]

Yes, it should unless the starter gears/springs are hanging up.

Thank you sir. I think I might just pull the starter to inspect & service it anyway seeing as she is now 34 years old...I'm slowing going through the old girl giving her some new life (pamco, pma, bronze swingarm bushes etc). Its been fun & quite therapeautic..

 

[XSLeo]

Just a quick run through of the safety relay and how it function. When you first turn the bike on, the S/R is in the untripped posiotion. When you push the starter button and the engine starts, the alternator starts making power, this power starts at zero volts and climbs quickly. When this voltage reaches about 4.5 volts,the S/R trips.
When The S/R trips it opens the contacts letting power flow to the starter relay, this stops the power flow to the starter relay. This stops the starter fromr running. On the later bikes it also closes the contacts that turn on the headlight.
The S/R turns the starter off faster than you can with you thumb. This prevents damage not to the starter it self but the gears that connect the starter to the engine.
The starters are pretty robust on these bikes. Seldom need fixing.
Leo

 

[retiredgentleman]

Just as XSLeo said, the starter motor themselves are quite rugged. When I said starter gears and springs, I meant the parts that are in behind the clutch.