Alternator swap - XJ/XS - wiring question

[Chuckster]

OK, I found a cheap stator, rotor and cover on e-bay from an XJ and am putting it on my '78 XS11 to provide more juice. All went well, plugging in the new stator, only to find the XJ stator only has 3 white wires coming from it (no yellow) while the plug on the XS harness has 4 wires (3 white, one yellow).

After researching on here, I learned that the yellow is used on the '78 and
'79's to run the headlight relay. This obviously changed in later models.

Question: is it as simple as splitting one of the 3 wires coming from the XJ stator into two, so I can feed all 4 wires from the harness? Can I just use a double bullet type connector to split? Does it matter which white wire I pick to split?

Thanks in advance to you electrical guru's!

[bikerphil]

According to an 80 and up diagram, the headlight relay trigger is run from the same white wire that provides signal to the tach. IIRC, the 78-79 have the needed diode inside the headlight relay.

[Chuckster]

I'm confused...

Apologize for my lack of electrical knowledge, but I'm still unsure how to connect the new stator...

[bikerphil]

Better wait for someone who has done this to chime in. I'd say hook the 3 fat white wires to the voltage regulator. Then tap into the thin white wire that goes to the tach and hook to the headlight relay trigger. Not sure if the voltage regulators for the XS and the XJ are the same though. You could always bypass the headlight relay (unplug and jump red/yel and blu/blk) easily so the headlight comes on with the key and not worry about the additional wire.

[Chuckster]

I kind of understand...

I understand what you're saying by using the feed to the tach to also trigger the headlight relay. Where exactly is the headlight relay and what does it look like? I have not really dug into the electrics on the bike, other than to clean connections. If this becomes too risky I may just go back to the original XS alternator.

[bikerphil]

The headlight relay is under the gas tank, in the center, up above the ignition coils.

[Chuckster]

Here's where I think I'm at...

I understand from researching this that the yellow wire from the alternator goes to the headlight relay. The yellow wire carries 6-7V, not the full 12-14V that the white wires carry, to activate the headlight relay. Since the XJ alternator no longer has the yellow wire, I need a work around.

This means that I have to activate the headlight relay another way, as Bikerphil suggested, by possibly using the wire going to the tach.

Or can I just leave the headlight relay unconnected? Since the '78E has a switchable headlight, can I just use the headlight switch?

Or should I do as suggested and unplug the relay and jump the red/yel and blu/blk wires?

Anyone try this?

[bikerphil]

unplug the relay and jump the red/yel and blu/blk wires?

Anyone try this?

I run both my Standard and Special that way. I know a few people have done this XJ alt. mod before, I just can't remember who.

[xj11john]

Does anyone know if an XJ alternator/Stator putting out 14.67 volts at times at high RPM is ok?

I just put a new stator and cover on mine and testing with my digital voltmeter did show that high at times and then would come down as I was holding the throttle steady at about 6000 RPMs.

[81xsproject]

I understand from researching this that the yellow wire from the alternator goes to the headlight relay. The yellow wire carries 6-7V, not the full 12-14V that the white wires carry, to activate the headlight relay. Since the XJ alternator no longer has the yellow wire, I need a work around.

This means that I have to activate the headlight relay another way, as Bikerphil suggested, by possibly using the wire going to the tach.

Or can I just leave the headlight relay unconnected? Since the '78E has a switchable headlight, can I just use the headlight switch?

Or should I do as suggested and unplug the relay and jump the red/yel and blu/blk wires?

Anyone try this?

If your interested, I know of a really cool circuit that can be built on the cheap for turning on the headlight. The circuit keeps the light off until the first time you put the bike in gear, then it stays on until the bike is turned off no matter what. I will probably be adding it to my bike if the new headlight project is ever finished.

[Chuckster]

Sounds interesting...

My interest kind of depends on how difficult it would be to assemble this circuit. I'm not real experienced with electrical, how hard is this to make?

[natemoen]

I think I would be interested in that headlight mod. could you pm me with it?

[XJOK2PLAY]

Does anyone know if an XJ alternator/Stator putting out 14.67 volts at times at high RPM is ok?

I just put a new stator and cover on mine and testing with my digital voltmeter did show that high at times and then would come down as I was holding the throttle steady at about 6000 RPMs.

XJ11John,
Don't mean to hijack the thread, but depends on at what time your checking... first starting, after cranking a lot and discharging somewhat, or constant well after hot??
Mine will do that right after startup, then drops to 14.1 going down the road.
Drops to 12.6 at idle. So it depends...

[trbig]

my digital voltmeter did show that high at times and then would come down as I was holding the throttle steady at about 6000 RPMs.

LOL.. I've tore up a few motors on these things, but even THAT makes me cringe! Not good on a motor to do that without a load on it. It shouldn't charge any more at 6k rpm than it does at about 2500-3k.

Reminds me of the drunks at a big bike meet here in Sparks, OK who like to.. for no apparent reason.. get out of bed at the camp site, crank up their Harleys at ohhhh... 3:30-4am.., and on a cold motor, just rap it up and hold it to the rev limiter (What.. maybe 3800 rpm? ) for a bit.. then shut it off and go back to bed.


Tod

[b.walker5]

Reminds me of the drunks at a big bike meet here in Sparks, OK who like to.. for no apparent reason.. get out of bed at the camp site, crank up their Harleys at ohhhh... 3:30-4am.., and on a cold motor, just rap it up and hold it to the rev limiter (What.. maybe 3800 rpm? ) for a bit.. then shut it off and go back to bed.
Tod

Worldwide problem, seems to be some sort of Harley ritual. Last rally I was at some guy in a tent a few doors down from me produced a paint ball gun and plastered a throttle happy clown just opposite me. Dude was drunk and it was dark so he had no idea where it came from, but it shut him up. Trouble is that when one does it it usually starts a pissing match and 6 other clowns start doing the same thing, and then some sports bike rider has to prove how much better his is and it goes on and on and on and on. I call it LDS. (Little Dick Syndrome)