too much spark

[Toolmaker Tim]

Yup, fair game, that's me.

[strippedFJ]

Have just gone over the way ignition coils / igniters work, and I'm betting on it being low level seepage from the coils primary winding to the secondary winding, resulting in the secondary constantly powering the plug (would be helpful to know if it's both or just one coil Lisa). When the TCI fires the coil you then get full power dump to the spark plug.

The TCI unit is basically an electronic switch which if fried would remain either open or closed, but would fail to switch.

If as MRO suggeted the spark is dropping when the starter is hit that would indicate a fried TCI, basically holding the coil in the 'fire' state. The spark would be weak because the coil isn't building a strong enough magnetic field. I don't know if the starter would cause the spark to pulse as there is always one cylinder on a compression stroke.

Hopefully Lisa will return and let us know what the problem was, assuming it gets fixed.

[randy]

In order to make a spark, the coil field has to collapse, just keeping the coil energized will not make spark. I've also never seen a TCI do what Lisa is describing, on it's own, but I have induced constant spark from a TCI on the bench by touching the amplifier input circuit with my finger. (The stray 60Hz voltage in the body is amplified). This is one of my troubleshooting techniques to determine which circuit is or is not working in the TCI, before or after the amplifier.

IF the TCI is truly doing what Lisa describes, the only reason I can think of is that there is major corrosion, dirt, moisture on the circuit board, causing feedback in the amplifier circuit(s).

I would welcome the opportunity to test that frankenstein, purely in the interest of science!

[prometheus578]

For those new members who don't know....
Randy is the guy to send TCI boxes to to have them tested or repaired.

[randy]

Thanks a pantload, Prom! Last time someone posted something like that, I got a dozen in the mail!

Seriously, though, if you do need help, PM me.

[Guy_b_g]

Don't know if this is any help at all or not...

I once installed an MSD HiFire ignition with a high performance coil on a built 360 in a Jeep J10. The jeep would run, (sort of) with a lot of backfiring from the exhaust and farting thru the carbs.

I ruled out everything else and decided it had to be the ignition.

Had my wife turn on the key to check the spark , and before it could turn over I was rewarded with a tremendous jolt that numbed my arm to the elbow.

Turned out that whenever the ignition was on the coil was firing...constantly.

I traced the problem to the two pickup wires that led to the module from the pickup being reversed... I switched them around and no more problem.

Could this be the problem here?

[randy]

Not familiar with the MSD system, or how it gets triggered, but ours is an inductive amplifier, no induction from the pickup (crank rotation) = no signal to amplify / spark. I still think that board is TCI corroded.

[lisa]

UPdated info

Here is the post:

Thanks for all the ideas, I'll try more tonight. Here's what I have:

Bike s/n number is 3j6?? I think... I looked up and it should be: xs1100sg

Just to clear things up: the constant spark is a dim or less spark than when the start button is pushed. when the start button is pushed it increases the spark to brighter than back to dim, and so on.

Bike must have a mind of its own; it no longer has a constant spark with the key on, but will just spark every once in a while with key on but nothing else happening. It makes a buzzing noise so I can hear it and look just in time the blue sparks in the plugs.

The plugs don't look to bad. They are not wet because I have gas tank off just trying to check spark first.

With all four spark plugs out: plugs 1 and 4 have the same thing happening, 2 & 3 have nothing either with the key or when the start button is pushed.

Wires look o.k., I don't see any bare wires or anything that looks broken or worn/torn.

Just a thought; Could this be cause by the charger on the battery? The battery tested weak not bad, so I connect charger to the battery and set at 20 amp. I know I'll need to replace battery, it does not what to hold charge.

Thank again, Lisa.

[randy]

Could this be cause by the charger on the battery?

YES!

If the charger is putting out enough AC, yes, it can cause it! have you tried jumping with a known good battery? Like from a car?

[lisa]

battery

Thanks, I'll try that. Lisa.

Also: I did buy clymer manual.

[barberad]

Not with the car running though. Just let the bike draw off the cars battery.

[lisa]

tested with battery

tested with battery and nothing... no spark at all. Must have been the charger sending the signals.

I'll keep testing. Thanks for the help!

[randy]

Lisa,

Start troubleshooting by cleaning connectors. Behind the fuse box you'll find connectors for the TCI pickups. Ditto at the TCI connectors on the box. After cleaning, test the pickup coil resistance, should be around 700 ohms, if I remember correctly.

[Ivan]

I have seen a few GM ignition modules fail in such a was as to present a constant spark. The frequency is so high that the spark plug whistles, no kidding.

The brighter spark when the starter is engages is because on older vehicles, especially those with breaker points, full voltage on the primary side would burn up points and coils. To cure this, they put a ballast resistor in the circuit to cut back the primary voltage to the coils. The starter solenoid had an extra wire that went to the primary side of the ignition, that passed full voltage to the coils while the vehicle was starting, for easier starts. when the solenoid disengaged, the voltage dropped again.

Since the XS uses hall effect (?) switches instead of points, I am not sure why the earlier models used a ballast resistor, unless the coils were wound to run with 8 volts.

[strippedFJ]

Re: UPdated info

Originally posted by lisa


Just a thought; Could this be cause by the charger on the battery? The battery tested weak not bad, so I connect charger to the battery and set at 20 amp. I know I'll need to replace battery, it does not what to hold charge.

Thank again, Lisa.

20 Amps is way too much power for recharging the battery. For motorcycles chargers should be around the 2 Amp charging rate. 20 Amps will result in overheating and fast deterioration of the battery.