XJ ignition on an 81SH

[trbig]

OK.. somebody explain to an electrical imbecile what I need to do to swap a set of XJ pickup coils for the stock SH setup? I've got several spares of XJ stuff and the timing curves are about the same on the '81 as it is my XJ.

So, I figure replace everything under the left sidecover. I know I'll need to wire in somehow the electronic timing advance and use an XJ TCI, but would it be a royal PITA to do? Would I need to re-wire the TCI plug..among other things?

The bike made me mad a couple weekends ago while I was laying on hot asphalt on the side of the road for a long time trying to fix the pickup coil wires with a pocket knife and zip-ties. This isn't a problem with the XJ's fixed pickup coils.

So be easy on me fellas.... explain things simply, and pretty pics would be awesome! lol.

[crazy steve]

I guess I'm the only brave soul....

Tod, it will be a bit finicky but definitely doable. You have most of the right wires in the right places already, you just need to move a few around and maybe extend a few, add one, and change some plugs.

I was going to post some pics, but I decided they really won't be that helpful as you can't 'see' that well with my photo skills...

You've got three plug connections that you have to deal with; I'll go over each one separately. All descriptions are looking at the harness plugs from the side the wires go into them.

At the TCI:

The larger plug is partially correct. Looking at the 8-pin plugs from the back facing 'up', you have on the XS: top- gray, white/red, black/white, blank, and bottom, orange, red/yellow, red white, black. The gray, black/white, orange, red/white, and black wires are the same for both plugs, no mods needed. You're lacking the wires for the vacuum switch, but have the 'leftover' wires for the ballast resistor circuit, the white/red and red/yellow. Use the white/red for connecting to the black/red at the vacuum switch. Now, this wire is spliced into the red/white power wire inside the harness, it may be easier to just run another wire. Move the red/yellow to the blank space and use it for the black/yellow, but again it will probably be easier to run another wire. In any case make sure these two pinouts aren't hooked to any of the existing XS wiring, only to the vacuum 'boost' switch.

The smaller plug you have options. None of the colors match, so you have to decide how 'close' to stock you want to stay. The pinout arrangement on the XJ TCI is different too, so again, how 'stock' do you want it? If you don't care, use this plug as-is and make all the changes at plug where the pick-ups connect to the harness. For reference, the XJ plug has the wires arranged thusly; left to right, top blank and gray, bottom black and orange, so if you get the matching pickup coil wires on those pins you'll be good to go.

At the motor:

First, you'll have to change either the plug on the pick-up coils or the plug in the harness; the XJ uses a 4-wire plug, the XS 6 wire. Once you decide this, then you have to pick the wires you need. This is where you need to pay attention. One caveat I'll throw in here is the XJ diagram doesn't identify which pick up fires which coil, in fact they don't identify the coils for cylinders at all that I could find; worst case it may end up 180 degrees out. So assuming that they kept the same logic in colors (orange and gray fire the same coil(s) on each bike), hook the pickups to the harness like this: The blue neutral wire is the same, so just make sure the two ends go together. The orange wire from the pickups, connect that to the white/red. Connect the gray wire to the yellow/red, and connect the black wire to the white/green. Before you fully commit to this, make sure that the white/green and white/red aren't connected inside the harness; these are the 'common' side of the XS pick-up coils, and if they aren't then do it this way. If they are connected, then use yellow/green for the orange wire from the pickups and you'll have to swap the yellow/green and white/red wires at the TCI plug.

One last wire; you need to run a 12V power wire from the ignition circuit (red/white wire) to the vacuum switch to power it. That should do the whole system...

Does your head hurt yet?....

[motoman]

I guess I'm the only brave soul....

Tod, it will be a bit finicky but definitely doable. You have most of the right wires in the right places already, you just need to move a few around and maybe extend a few, add one, and change some plugs.

I was going to post some pics, but I decided they really won't be that helpful as you can't 'see' that well with my photo skills...

You've got three plug connections that you have to deal with; I'll go over each one separately. All descriptions are looking at the harness plugs from the side the wires go into them.

At the TCI:

The larger plug is partially correct. Looking at the 8-pin plugs from the back facing 'up', you have on the XS: top- gray, white/red, black/white, blank, and bottom, orange, red/yellow, red white, black. The gray, black/white, orange, red/white, and black wires are the same for both plugs, no mods needed. You're lacking the wires for the vacuum switch, but have the 'leftover' wires for the ballast resistor circuit, the white/red and red/yellow. Use the white/red for connecting to the black/red at the vacuum switch. Now, this wire is spliced into the red/white power wire inside the harness, it may be easier to just run another wire. Move the red/yellow to the blank space and use it for the black/yellow, but again it will probably be easier to run another wire. In any case make sure these two pinouts aren't hooked to any of the existing XS wiring, only to the vacuum 'boost' switch.

The smaller plug you have options. None of the colors match, so you have to decide how 'close' to stock you want to stay. The pinout arrangement compared to the 2H7 TCI is different too, so again, how 'stock' do you want it? If you don't care, use this plug as-is and make all the changes at plug where the pick-ups connect to the harness.

At the motor:

First, you'll have to change either the plug on the pick-up coils or the plug in the harness; the XJ uses a 4-wire plug, the XS 6 wire. Once you decide this, then you have to pick the wires you need. This is where you need to pay attention. One caveat I'll throw in here is the XJ diagram doesn't identify which pick up fires which coil, in fact they don't identify the coils for cylinders at all that I could find; worst case it may end up 180 degrees out. So assuming that they kept the same logic in colors (orange and gray fire the same coil(s) on each bike), hook the pickups to the harness like this: The blue neutral wire is the same, so just make sure the two ends go together. The orange wire from the pickups, connect that to the white/red. Connect the gray wire to the yellow/red, and connect the black wire to the white/green. Before you fully commit to this, make sure that the white/green and white/red aren't connected inside the harness; these are the 'common' side of the XS pick-up coils, and if they aren't then do it this way. If they are connected, then use yellow/green for the orange wire from the pickups and you'll have to swap the yellow/green and white/red wires at the TCI plug.

One last wire; you need to run a 12V power wire from the ignition circuit (red/white wire) to the vacuum switch to power it. That should do the whole system...

Does your head hurt yet?....

Uhh.......believe he stated SH Steve.....4RO not 2H7........whether or not that's gonna make a difference in the conversion, but wire colors may for explanations sake.......

[BA80]

The XJ doesn't have a vacuum advance so does it still have the flexible wires?

Dammit Tod! If you just would have stopped here I have a good set. We could have had them swapped out in about a half hour.

[crazy steve]

Uhh.......believe he stated SH Steve.....4RO not 2H7........whether or not that's gonna make a difference in the conversion, but wire colors may for explanations sake.......

My mistake in naming the TCI, and I'll admit I haven't personally checked the pinout on the 4R0 box, but the wiring diagrams show all the same wires/colors for both the 2H7 and 4R0. It might pay to check the pinouts to make sure they're in the same place on both. I'll edit my post to correct what I may have overlooked...

[DGXSER]

One thing you mentioned Steve is a wire for the ballast resistor which the 4RO does not use. I'll try to photo my TCI later tonight or tomorrow for pinout.

[crazy steve]

Take a picture of the wire plug; the TCI's are all the same in terms of pins on them, just some don't get used depending on the model. The five in the larger plug that seem to be consistent are the coils (orange, gray), tipover switch (black/white), power in (red/white) and the black (ground). I physically compared the XJ and a XS harness of an unknown year. I have three loose harnesses here and that part of the wiring is all the same. One harness is supposedly off a '81H, but that bike was a mish-mash of parts so whether or not it was original is anybody's guess...

As far as the pick-up coils, they're the same on the '81 ignition at the motor as all the earlier bikes with the same 2H7 part numbers. You've got an orange, gray, and two blues (some have reported only one) which would be the 'common' for the coils.

[bikerphil]

Not sure if I understand correctly but can't the XJ pick up coils just be wired into the stock 81 TCI, without changing anything else?

[crazy steve]

They're a different ohms value, so I don't think I'd try it. The XS are 720 ohms, the XJ is only 120....

[bikerphil]

They're a different ohms value, so I don't think I'd try it. The XS are 720 ohms, the XJ is only 120....

Ahhhh. Gotcha.

[trbig]

The XJ doesn't have a vacuum advance so does it still have the flexible wires?

Nope.. nothing moves in there. The advance is all done electronically. The vacuum line on the #2 carb is attached to a little black box on the frame that sends the vacuum readings to the TCI. Just regular wires and a hard plastic insulation over them like the rest of the wires in the harness.


Thanks Steve. Looks to be a bit more involved than I'd hoped just to keep from splicing wires. Looks like I'll probably just go to Harbor Freight, buy a cheap multi-meter and steal the flexible lead wires.

It just seemed kind of weird where the wires actually broke. It was back under the braided wire insulation almost to where the wires go through the case. Moving the timing advance, it didn't look like the wire had any tension there or was even moving there? The insulation that covered the wires was like a soft rubber. I could strip the wires with just a fingernail... like they'd been sitting in carb cleaner or something... about a step or two above a piece of penny bubble gum that's been chewed on a while. lol. I guess that's just so they stay flexible?

And Greg, I appreciate the offer. I'll just try splicing these first before I steal even MORE parts from you. What I will need, is a nice closeup pic of how the wires were tied down in there OEM. I didn't have any electrical tape with me, so I ended up using gobs of zip-ties close together over each wire splice to keep it insulated from the other... then kind of tucked it around in there to keep the wires off the timing wheel.