test #1 = 12.11 V
#2 = 0.75 V
#3 = 0.003 V
#4 = 11.34 V
#5 = 12.10 V
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The coils (including replaced one) are all Gills. Since I simply can't afford to replace them as yet (it would hurt financially and emotionally if they didn't fix the problem), I'll be more than willing to investigate all other possibilities in the meantime.

What the current prognosis, doc?

kyre don't be so afraid of replacing the coils if that's the problem . less than $200 for all three del . http://nologyhotwires.com/


jimmyj's the guru of stuff like this so just sit tight .

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Originally Posted by kyre_kyre

#1 = 12.11 V #2 = 0.75 V #3 = 0.003 V #4 = 11.34 V #5 = 12.10 V ------------------------------

The first and last tests checked the condition of the battery with the headlight and ignition system as a load. That looks good, so your battery is OK.

The second test checked the condition of the wiring and switches from the battery to the igniter module and that's looking very good. (Better than my bike!)

The third test verified the quality of the system ground and that looks fine too.

The fourth test verifies the results of the second and third tests and eliminates errors of meter accuracy. Add #2, #3 and #4 and that should total the battery voltage. You're only 0.02 volts off so that's well within the limits of accuracy of your meter.


The symptom you gave -- that the engine shut off at an idle like a switch flipped rather than slowing down and quitting -- and also that nobody could find the problem led me to suspect that the series resistance from the battery to the igniter and from the igniter to ground was high enough that it was switching the igniter off.

The Gill ignition appears to shut down someplace between 5 and 8 volts AND there's about 12 feet of wire with over 40 electrical connections between the battery and igniter. That wire length and all those connections made that a prime candidate for high resistance. It's also a problem that your average bike shop would probably never find.

The good news is that there's not enough of a voltage drop through the system to cause an igniter shutdown. Your voltage drop is about 1/2 the drop on my bike and I'm not having a stalling problem, so you don't have to take the wiring harness, switches and connectors apart.

It was a bit of a long shot but had the benefit of verifying the condition of the electrical system.


The next step is to go to basics and test the coils.

Make sure your battery is fully charged first, then hang a spare spark plug from each of the ignition wires (one at a time) and apply a good ground to the big end of the spark plug. (I use a car jumper/booster cable to the base of the footpeg.)

Crank the engine and look at the spark. If it's thin and yellow then it's a weak spark. If it's fat and blue it's a good spark.

It's common on these engines to have one coil fail and go weak. Two coils bad usually means the idle gets rough enough that either somebody replaces the coils or hauls it off to the shop for repair. Three coils bad at once happens occasionally too.

The problem is that these coils rarely fail completely with no spark.. They go weak but still fire adequately at higher rps where the alternator supplies power. The lower battery voltage at an idle makes the weak coils visible.


So the battery looks good, the wiring is in good shape and a coil test comes next.

Jim

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I charged the battery (initially it settled around 13.2V) and tested spark from all of the plug wires.... twice... on each cyclinder. All three had strong and consistent spark as I turned the engine over. I was a little curious as to why it took a second or two for the spark to show after hitting the starter, but once it came on it looked wide and bluish like you said. Made the tests and then through the charger back on the battery. A little disappointed in a way that I didn't find anything wrong here. [I did have the thought that the stalling almost always happens once the bike is warmed up, so heat was one factor that I couldn't introduce without hooking up an auxiliary fuel supply and running it on two cylinders] Well, the lesson here is that with a cold engine the coils "seem" to be just fine. Is it time for me to get that thin-walled plug socket now?

Hey, this is starting to sound like the Ignition Pick-Up,
It comes out of the right side of the engine in that "teardrop" shaped cover. If the carbs have been off once or twice then check the wires that run from the engine cover to a white? plastic connector that is under the airbox/seat area which connects to the wiring loom.
the 2 wires by the plastic connector are a bit delicate and can be loose or damaged by pulling the carbs if your (or your mechanic) arent careful.
Hope this helps.

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Since all three had a fat blue spark you're OK on the coils. The symptom of a bad coil is a random misfire on one cylinder that disappears when the alternator takes over for the battery. The failure mode of the coils is that the secondary windings short together and reduce the output voltage.

Since you've said your idle was smooth I didn't really think the coils were the problem.

The reason it takes a second or two before you get a spark is that the ignition plate on the crank has 7 teeth so it takes a full revolution for the igniter to find the #1 tooth. Then it just keeps count.

I'm still disturbed by the 'cuts out like a switch was thrown' thing. Bad coils don't account for that and an intermittant in the ignition circuit would show up as a random misfire at higher rpms. You wouldn't fail to notice if the ignition quit briefly at higher revs since the crank would have to do it's full revolution thing before the igniter got oriented and started firing again.

For a thinwall socket, buy cheap! The cheaper it is, the thinner the sidewall generally is. The 6-point sockets also seem to have thinner sidewalls than the 12-point ones.

I'm still thinking about this... I wish I could get my hands on the bike for a few minutes to get the feel of it.

Jim

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...perhaps I'll send it to ya, Jim... one piece at a time...

It still looks like an intermittent electrical problem to me, just to follow up the advice Jimmy has given you have you checked to see if the spade connectors on the coils are a tight enough fit ?

Also check the plug leads where they fit into the plugs, nothing burnt around there ? which may be a poor connection caused by arcing ?


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Ride on !

So what's the latest situation on this ? have we given up ?


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Ride on !

I think I may be too stubborn to give up. I'm still looking for a small enough plug socket...not proving to be easy...even though it's so unlikely that (after seeing good coils) a goofy plug could stall out the bike under 2K, yet run fine at all other speeds. I've been checking every connection point I can discover...plug wires, coil feeds, wiring harness...everything so far has been clean and tight...and if it was just medium tight, it became nicely tight before I reconnected it. I haven't yet traced the ignition sensor feed as someone suggested, but I will. Does anyone know what ohms it should read across the sensor?

I'd like to get the ignitor dismounted from the battery box (how is this done?) so I could hold it in my hand and slap it around while the bike was running...yes, I'm down to the "technical tap" mentality. My goal now is to rig an aux fuel system (my uncle calls this the motorcycle I.V.) so I can run it without the tank on and start carefully poking around while its prepped for failure.

Nope...haven't given up yet....but the longer I go without finding something wrong, the more I might want to....