Possible weak spark?

[BillyRok]

I haven't messed with my XJ much since fall harvest last year but now that it appears this miserable winter may finally be loosening its grip and the rain is washing the sand and salt from the roads I'm getting the itch to ride.

Last fall I was having some difficulty getting the carbs synched with my carbtune, the motor wanted to stall when trying to idle it in the 7-800 rpm range, and some opinion was that maybe I was having an ignition issue. Voltage reads 12.2v at the battery and 10.7v at the 2 connectors that plug into the coils. This is not good true? Was told that power path is battery - ignition switch - ignition fuse - kill switch - TCI - and finally coils. I have TC's fuse box installed and cleaned the ignition switch (which didn't look too crudded up). Can't remember if I cleaned the kill switch or the TCI connector so I will check those. Coil specs are 2.5 ohms +/- 10% on the primary (mine currently read 3.2 ohms) and 11k +/- 20% on the secondary (mine currently read 11,120 ohms).

First question/concern is going from 12.2v at the battery to 10.7v at the coils is a bad thing right? Could this cause a weak spark? Is the only cause dirty connections?

The other question concerns the coils. 3.2 ohms on the primary is out of spec, does this cause a weak spark? What happens to the resistance numbers as the coils age and how does that affect how they perform?

Thanks for any information and advice you can offer.

[crazy steve]

First question/concern is going from 12.2v at the battery to 10.7v at the coils is a bad thing right? Could this cause a weak spark? Is the only cause dirty connections?

The other question concerns the coils. 3.2 ohms on the primary is out of spec, does this cause a weak spark? What happens to the resistance numbers as the coils age and how does that affect how they perform?

Yes, the low voltage at the coils isn't helping at all. You won't get full battery voltage at them for various reasons, but it shouldn't be down more than about a volt, so clean connections until it's better... Look here for how to check them:
http://www.xs11.com/forum/showthread.php?t=35339

The coils should be less of an issue if you get the voltage to the coils up. Yes, that's a bit high on the primary and will result in a bit less output, but with adequate primary power they should still be 'ok'. I wouldn't replace them until you had the voltage fixed, at that point if you're still having issues then I'd look at new coils.

[oldyam80sg]

Just curious are you getting 12.2 volts without engine on or bike running? Battery voltage running should be higher than 12.2 volts while running.

[BA80]

800 is a pretty low idle. Mine won't idle very well under 1000.

[BillyRok]

This was the suggested method I followed (thanks Motoman) so the key was on but the bike was not running.

Key on, voltage at battery on pos/neg. term. for a base. Key still on, ground of meter to the three grounding wires/screw on voltage regulater hold down(this uses actual frame grounds as rest of sysyem does instead of from battery). Positive meter lead to each of the red/white stripe wire of coil plug-ins under tank(with key still on). Report the voltage first on battery(for a base voltage), then at those coil wire plug-ins for comparison(with key still on).

Hope to do some checking of the electrics this week based on info in Steve's post. We got 6" of wet heavy snow last night so I guess riding season is still a few days away. And I bought a new multimeter for about $25 that didn't work after I got it home so I had to take it back for a replacement...give you one guess where it was made.

[pete_s]

Love my Craftsman little red meter. less than $25 and I can't kill it.

The leads are a little plasticy, stiff, and I use it most days at work. The meter I have is about 3" X 5" with a large display, a 25 amp current range, and a plug in thermocouple for temp reads in C and F. Auto ranging is perfect and fast. I bought 2 for my kids w/o the temp sensor for Christmas @ less than $14 on sale.

My regular work meter is a $450 Fluke and I hate it.

If you get a meter like this with a high current range plug, put a piece of masking tape over it. I accidently took down a computer room at a hospital shorting a outlet. I changed the fuse in the meter and it still works!

[pete_s]

My XS1100E service manual shows the correct wiring diagram, circuit as

1. Battery
2. Ballast Resistor
3. Coil
4. TCI
Circuit may have been changed in later years???
So I would expect much less than 12v at the coil because of the ballast resistor. With the engine running, avoid testing across the coil and go to chassis ground instead.

Interesting test using the in the manual electro tester is it says if the spark can jump 6mm or .24 in your ignition is ok. Make sure adjacent plug lead is grounded as the manual says there is a big strain on the coil insulation with trying to make a spark across a big gap!

[DGXSER]

The 78-80 models have the ballast resistor. That is due to the coils being 1.5 ohm coils and the rest of the system working on 3 ohms (TCI Basically). In 81 Yammie put 3 ohm coils in , so the BR went away.