Electrical analysis

[Incubus]

As I forge ahead, still manual-less, I was hoping y'all could help me analyze my ignition. I tried kicking it and got no spark, although I had a jumper battery hooked up as a power source. I dn't make much of that, yet, since I haven't cleaned all the connections yet, the spark plug caps are very old and were exposed to the weather without plugs for several years and, of course, there is no top end on my cycle yet. But I have taken the following measurements:

From field coil, white wire to white wire, all three readings were .7 ohms resistance. I read on the tech tips site I should be looking for .4 ohms, but since they were all the same reading and because they were measured within an ancient analog engine analyzer, allowing for the native resistance in the measuring device I figured they were pretty much spot on.

All alternator measurements were made on this ancient device. Have you ever seen a picture of Stonehenge? That is the schematic for the updated version of engine analyzer the ancients were working on. It is old. Anyway, back at the ranch:

Green wire to brown wire- 4.5 ohms. Again, I figure that's close enough for government work.

At this point I switched to my much more modern Craftsman digital ohmmeter, which is too sensitive for the alternator tests.

Pickup coil wires yellow/green to yellow/red - 764. White/green to white/red 775. Should they be that different? When I rotate the vacuum advance at one point on one side there was a slight shudder of three points (764 to 767) momentarily, but I was unable to duplicate it when continued to rotate the advance.

Spark plug wire to spark plug wire - one side I got a reading of 15.1. The other side was 18.4. Resistance between the orange and grey wires leading into the coils, 3.3. Should my coils be a concern?

The easy way to check the ignition would be to start te bike, but it's a long way to that so I am stuck doing static tests and trying to understand the specs of the machine.

Can anyone analyze these readings and tell me what you think?

Also, does someone have a crappy wire harness that has a good eight wire plug for the ignition unit. Mine may still eb functional, but it is crumbling.

Thanks,
Patrick

[TopCatGr58]

Hey Patrick,

Were your coil readings done with the caps OFF or ON? Without the caps, the range should be 13.5K to 16.5K, so 18 could be a little high, but the primary readings sound right at 3.3 ohms!

That wasn't much of a fluctation with the PU coils, but what you want to do is pull on the PU wires while taking the readings, then if it doesn't fluctuate a lot, then they should be okay!

There is a link to Randy's Page which has info on how to test the TCI statically. Aside from the TCI, it sounds like it should produce a spark.

Remember, the spark has to travel thru both ends of the coil's high tension leads. SO you need to have a spark plug fitted into BOTH ends of the coil you are testing, and touching the frame/case so that the power can come from the center electrode, jump the gap to the electrode to the frame, then from the frame to the OTHER spark plug, rim electrode, and then into the center electrode. If both plugs were not plugged in, then the circuit wasn't complete, and that's probably why you didn't see any spark!
T.C.

[HobbyMan]

What T.C. said. Also, check your TCI connections. You said that they were crumbly. When I rebuilt my 80G it was crumbled so that one terminal was sliding out of the plug. Temporarily, I used liquid electical tape to glue it into the plug. Later I regreted doing that because it took forever to clean off while switching plugs. I would suggest spending time cleanng off all of the connections before making any serious deductions as to electical integrity.

[Incubus]

Thanks, guys. For what it's worth, I yanked the caps off the spark plugs before I took the readings. The 1 and 4 caps will never go on any spark plug wires again. They are in bad shape. Two and three I put back, only so I could see at a glance which coil they belonged to.

And you are right, TC. It was Sunday, the game was on, I forgot I need plugs in both wires to get a spark. It probably also would be helpful to have caps a spark can make it through.

If I stumble onto some good aftermarket coils, how much ohmage would I want? I saw a post from an XSer who switched to Dyna 1.5 ohm and he loved the way they made the bike run, but he also complained that it made it harder to start. Any thoughts on this? I could go 2.2 ohm, 3 ohm or even .7 ohm, and that's just Dyna...

Thanks,

Patrick

[randy]

With ballast resistor = 1.5 ohm coils

No ballast resistor = 3 ohm coils.

DO NOT USE .7 OHM COILS, you'll be shopping for a new TCI.

[TopCatGr58]

Aftermarket coil source!

Hey Patrick,

Here's a copy of a message I posted a while back, and you can shop for the plug caps and replacement wires while you're at it!
**********************************************
Hey Folks,

Been shopping and comparing stuff on MikesXS, and found an interesting item. In the 80-84 model 650's, they went to the TCI style ignition, and so the replacement coils for them are dual posts....waste spark style, and have same Ohms as the 81-82 series XS11/XJ11. The mounting holes are 90 degrees off from how the XS11 mounts vs. the location of the high tension outputs, but they are a darn sight CHEAPER ($28.00 ea!)than the Accel or Dyna aftermarkets, don't need a ballast resistor....so with the 78-80's, just bypass the resistor. Here's a model # and picture: Part #17-6803

High Output Replacement Ignition Coil - for 80-84 XS650’s with Factory TCi ignition (dual lead - 1 used per bike ). Used on 80-84 models Only, and is Not for contact point systems. Mounts to stock brackets. Plug Wires not included. Not for use with Boyer Ignitions. Mount this coil to stock bracket on opposite side and with high tension plug wires facing to front of bike ( Red/White wire from stock harness goes to + terminal on coil).

That was the description text from Mike'sXS. Ours mount with the leads to the rear.
Just add leads and plug caps, and they should be fairly plug and play! Just an FYI...and possible future tech tip/link!



Alternative Ig. Coil thread.

[Incubus]

Cool. I see new coils in my future.....