Ignition Rebellion

[thur94]

Hi all. Have an interesting issue with my 79 xs1100. Cylinders 2&3 have no spark. I've tested resistance across the entire circuit, from pickup coil to CDI box, CDI box to coils, coils themselves, all checks out. If I swap wires from the cdi to the coil for 1&4 to 2&3, the problem moves to 1&4, so the coil for 2&3 is obviously working, just not receiving power. I even swapped out the CDI box (I know these never break but with everything else ruled out I gave it a try) and the problem still persists.

I should also mention that a PO has done wiring work on the pickup coil before using the soldering trick discussed here for broken wires.

With resistance checking out across the entire circuit, what am I missing? It seems like everything is working how it's supposed to... But just doesn't? Help!

[Tonyxs11]

have you checked the flexible wires at the ignition advance ? they tend to snap under the insulation with constant movement.

[thur94]

Yes, 700 ohms resistance 😔

[LAB3]

Not the coils, the wires themselves. If you're reading 700 ohms in the WIRES then something isn't right.

[Tonyxs11]

Yes, 700 ohms resistance 😔

grab hold of the wires one at a time and stretch them, if the wire inside is broke the insulation will stretch.

[LAB3]

grab hold of the wires one at a time and stretch them, if the wire inside is broke the insulation will stretch.

Yep! Even if they aren't all the way separated it's enough to keep them from doing their job. Following that exact advice I found a spot where the copper inside the insulation was like power, after cutting and crimping them together the problem went away.

It was advised here on this forum not to use solder since the heat could damage those super fine copper strands, I undid my previous soldering and crimped that spot then put shrink wrap over it to insulate and assure holding it together.

[thur94]

The wires at the pick up coil, correct? I didn't see any additional breakage, and I'll attach pictures of the repairs from the PO. I pulled off the heat shrink to make sure the repair was still in good shape and it looks alright to me.
If there was an additional breakage somewhere else in the wire, I wouldn't be able to read any resistance across the pickup, right?

[LAB3]

With an ohm meter you're sending a small voltage with minimal amperage through those wires, in operation both V and A are going to higher. Follow Tony's advice on checking them out, it's a very well documented problem with the XS and is the most likely place to look after following the steps you described.

[thur94]

Assuming there is an additional breakage and given that the wire has already been patched twice before, how easy is it to just redo the pick up with new wiring?

[LAB3]

Not hard to rewire, finding a replacement is tough, they're out there and when they pop up they go for a premium price. Check eBay, they're closely traded between friends and acquaintances here.

[bikerphil]

You could also check the P/U coil gaps, .027" at the reluctor tab.

[DEEBS11]

One of these Hall Effect sensors is probably bad. Perhaps the previous owner assumed the wire was bad and made the repair which did not fix the actual problem. There is a set here on eBay for stupid money. Also be advised that sometimes measuring a circuit at rest may give different readings under load (such as a running vibrating engine).

https://www.ebay.com/itm/29532530480...Bk9SR6bG1e3vYQ

[DEEBS11]

This one is more reasonable. I have used this seller several times.

https://www.ebay.com/itm/38539740422...Bk9SR6jG1e3vYQ

[andreashweiss]

good morning, in case anybody needs a complete pickup coil assembly. I have one left, off 79sf, send me a PM, to discuss or call as I do not check email every day. no text.... 1 2five0 49five 344five. thanx andreas

[motoman]

thur94, p/u coil wire replacement can be done using the small insulated wireing from an old dial type telephone.