Question about testing coils

[vcgodinich]

Rebuilding a bike, decided to replace the coils with the ones from mikexs... the green ones.

Tested them, they spark fine. About a week later, cylinders 1&4 have no spark. Switched orange / grey wires, still no spark on 1&4, but 2&3 still have spark, so electrical up to the coils is fine.

Took off the questionable coil and ohmed across the primary coil, ~4 OHMs. Across the secondary ~14k. Primary to secondary is open.

So that all seems like the coil is good...

Put it back on, turned on the key and there is 12v between ground and orange/grey and also 12v between redwhite stripe and ground. So that seems normal, right?

All I have switched spark plugs and spark plug wires, so that is not the problem.

So is my new coil just toast, or is there something I am just overlooking?

[DAVINCI]

Re-solder the TCI pins.

Look here:

http://www.xs11.com/forum/showpost.php?p=390226&postcount=14

[fredintoon]

Rebuilding a bike, decided to replace the coils with the ones from mikexs... the green ones.
Tested them, they spark fine. About a week later, cylinders 1&4 have no spark. Switched orange / grey wires, still no spark on 1&4, but 2&3 still have spark, so electrical up to the coils is fine.
Took off the questionable coil and ohmed across the primary coil, ~4 OHMs. Across the secondary ~14k. Primary to secondary is open.
So that all seems like the coil is good...
Put it back on, turned on the key and there is 12v between ground and orange/grey and also 12v between redwhite stripe and ground. So that seems normal, right?
All I have switched spark plugs and spark plug wires, so that is not the problem.
So is my new coil just toast, or is there something I am just overlooking?

Hi VC,
Just maybe you missed a step?
You say Switched orange / grey wires, still no spark on 1&4, but 2&3 still have spark,
But you DIDN'T say you swapped the plug wires to match.
Swapping the orange and grey wires without swapping the plug wires to match puts the coils 180º out of phase but don't change which plugs the coils fire.

[natemoen]

Re-solder the TCI pins.

Look here:

http://www.xs11.com/forum/showpost.p...6&postcount=14

Good to see you back here again Randy!

[vcgodinich]

Hi VC,
Just maybe you missed a step?
You say Switched orange / grey wires, still no spark on 1&4, but 2&3 still have spark,
But you DIDN'T say you swapped the plug wires to match.
Swapping the orange and grey wires without swapping the plug wires to match puts the coils 180º out of phase but don't change which plugs the coils fire.

I was pulling the plugs out, grounding them and looking for a spark, not trying to actually start it. It should have sparked, unless I am just missing something here...

[GLoweVA]

Make sure that both plugs of the pair are touching the engine.
These bikes use a wasted spark system and both plugs spark at the same time and in order to complete the circuit, both plugs need to be grounded.
Also check to make sure the gaps are good too.
Are you checking your secondaries from the plug cap to plug cap?

[vcgodinich]

Make sure that both plugs of the pair are touching the engine.
These bikes use a wasted spark system and both plugs spark at the same time and in order to complete the circuit, both plugs need to be grounded.
Also check to make sure the gaps are good too.
Are you checking your secondaries from the plug cap to plug cap?

Yes, I had the other 3 plugged in at the time, and would only test one out, grounded.

The gaps are good, I switched spark plugs to one from the other cylinder that I know sparks fine.

Will check cap to cap... I was just testing at the coil. Good idea.

Checked cap to cap, same ~14k.

[GLoweVA]

If you've got stanndard resistor caps, those can get a little corroded inside.
If you look down into the hole you'll see a slot for a flat head screwdriver, you can then unscrew it and the resistor and spring should fall out.
Clean it up with some rubbing alcohol or carb cleaner and a q-tip. (or de-oxit if you've got some)

Another faulty place is the wire end where the cap screws into the wire.
The wire can get a little corroded too, the fix there is to trim off about a 1/4" of the wire and screw the cap back on.

Okay, not the best pic in the world, but at least it shows you that the plugs do indeed come off the wires:

[vcgodinich]

Re-solder the TCI pins.

Look here:

http://www.xs11.com/forum/showpost.p...6&postcount=14

Question before I go melting things... if the TCI was bad, wouldn't swapping the orange / grey cables make the "bad" coil work? Because it didn't in my case. And the other coil worked with the swap, so wouldn't that mean that the TCI is working fine?

[GLoweVA]

Yes, I had the other 3 plugged in at the time, and would only test one out, grounded.

The gaps are good, I switched spark plugs to one from the other cylinder that I know sparks fine.

Will check cap to cap... I was just testing at the coil. Good idea.

Checked cap to cap, same ~14k.

Just saw that last line:
So 14K cap to cap, that's good, so either the TCI isn't telling the coil to fire, or the pick up coil aren't telling the TCI to fire.

[vcgodinich]

If you've got stanndard resistor caps, those can get a little corroded inside.
If you look down into the hole you'll see a slot for a flat head screwdriver, you can then unscrew it and the resistor and spring should fall out.
Clean it up with some rubbing alcohol or carb cleaner and a q-tip. (or de-oxit if you've got some)

Another faulty place is the wire end where the cap screws into the wire.
The wire can get a little corroded too, the fix there is to trim off about a 1/4" of the wire and screw the cap back on.

Okay, not the best pic in the world, but at least it shows you that the plugs do indeed come off the wires:

I am using the XS coils... and the caps that came with them. As I understand it, they aren't resistor caps. All of the connections are new, and worked for a time, and I have looked them all over. I did an OHM reading of the secondary through the cables, so wouldn't that rule out any problems with them?

[GLoweVA]

Question before I go melting things... if the TCI was bad, wouldn't swapping the orange / grey cables make the "bad" coil work? Because it didn't in my case. And the other coil worked with the swap, so wouldn't that mean that the TCI is working fine?

Make sure that the red/white wire has a good connection from the coil back to the TCI.

[GLoweVA]

If the secondaries are ohming out good and the primaries too, then the coil isn't getting the right voltage from the TCI. You swapped the orange and grey, but the coil needs a 'return' path ie the rew/white. Check that connection.

[vcgodinich]

Just saw that last line:
So 14K cap to cap, that's good, so either the TCI isn't telling the coil to fire, or the pick up coil aren't telling the TCI to fire.

Yeah, but using the other wires (orange / grey) that I know are working, it still doesn't fire.

[vcgodinich]

If the secondaries are ohming out good and the primaries too, then the coil isn't getting the right voltage from the TCI. You swapped the orange and grey, but the coil needs a 'return' path ie the rew/white. Check that connection.

I looked it over and it seemed okay. I checked the fork place.

If it were the return, I shouldn't be able to measure ~12v at the orange / grey when the key is on, right? Or are you saying to do a loop test from the front red/white to the back red/white at the TCI? If that were bad, wouldn't both coils not work?