1981 XS1100 Midnight Special Slow restoration

[Mathh]

I can't recall a triple with YICS. Looks more like a small Maxim or Seca to me. Not that it is important

[bikerphil]

I can't recall a triple with YICS. Looks more like a small Maxim or Seca to me. Not that it is important

Yep, you're right Mathh, it is an XJ small 4 cyl.

[Medumdum]

Unplug the 4 pin connector on the TCI and check for 720 ohms between pairs while jiggling the wires down at the ignition plate. They usually break internally where they are clamped. That video you posted is for a 750, 3 cylinder which is different.

Tried it, jiggled the hell out of all the wiring on the pickup coils and both connections read a constant 730-740 ohms. Even cranked the bike, resistances changed a bit but never went over 1k or dropped below 600. I even checked the resistances of the ground wire to ground on the battery while jiggling the cable, got about 50-60 ohms on both as well. So at this point I’m assuming it’s the pickup coil, but would there be any other way to test the pickup coil itself?

[DEEBS11]

This is how.

[bikerphil]

You mean it may be the ignition coil, you were just testing the pickup coils. Another place to look is the solder joints inside the TCI, sometimes they crack where the 4 pin connector attached.

[DEEBS11]

This is the area.

[Medumdum]

You mean it may be the ignition coil, you were just testing the pickup coils. Another place to look is the solder joints inside the TCI, sometimes they crack where the 4 pin connector attached.

Ah, thought it just tested the wiring and there was a chance the pickup itself wasn’t picking up the signal from the rotor. When I swapped the coils both sparked, and resistances were all in spec, so I think those both have to be good. I took a quick look at the TCI and nothing looked obviously broken but I’ll try and test those pins.

[Medumdum]

This is how.

Interesting, I’ll check out the voltages on the TCI make sure they’re good.

[bikerphil]

Yes, and make sure the battery voltage is up to snuff or the TCI won't fire properly.

[Medumdum]

Finally got a new battery in a few days ago, trickle charged it overnight and still the same, still only spark on 1-4, even when switching coils, pickups. Did a oil change and ngk plugs while I was waiting for the battery, so those are fresh. I’m pretty sure it’s the TCI by now, but I have no idea what I’d need to do to repair it. I’ve done soldering plenty before, but only when someone/something is telling me what to test/solder. I can’t seem to find a guide to repairing the XS1100 TCI specifically. I’m probably going to try and actually open it up now to look at the board, since it looked like I have to desolder the pins to actually get it out of the box.

I’m picking up a parts bike that the PO of this bike offered, no tank or plastics just frame, bad engine and electrical, but hoping the TCI is still good, and it won’t hurt to have spares. Won’t be able to pick it up till next Sunday, so if I can fix the TCI in the interim all the better.

[bikerphil]

The first picture in post #36 shows where the P/U coil connections are, make sure there is no broken solder joint there. There is a red circle identifying the 4 connections.

[DEEBS11]

[Medumdum]

I assume I test that just by touching the joint and the pin with the multimeter leads set on continuity? They all beep, and read 0.0 ohms. Checked the other connector and those are all also good. I’m out of flux so picking some of that up, cuz I’m assuming I have to desolder the pins to the the board out of the actual case to look for any broken caps.

[DEEBS11]

I had one of these apart a few month ago and everything inside is coated. Not really serviceable with standard solder equipment. You really need professional tech equipment & conformal coating removal equipment. You should just delicately touch up the solder on the plated through holes shown in the picture without overheating the joint. Opening that unit up will give a high degree of incurring more issues. The problem is more than likely in your ignition sensors or harness as this is a more common problem. Problems with the TCI are very rare with the exception of cold/cracked solder joints. A non-invasive way to test this is to plug in your second spare TCI from the parts bike and see what happens. No risk of further damage in that test.

I re-read this thread and you did measure 735 ohms at the sensors which is good.

[Medumdum]

Dang, I’d head rebuilding some other TCIs wasn’t too difficult. Guess I’ll update y’all in a week or so once I grab that parts bike.