ignition question
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Cruiser
Joined: Jan 2008
Posts: 161
Likes: 1
ignition question
On my 79 I've noticed it runs on one cylinder at times. You can pull plugs and plug them in (outside cylinder)and crank-and sure enough one will not be firing. You can swap the two plugs and it still will not fire in the otrher location (which tells me its the plug and not ignition-so I thought). Tried screamin eagle plugs-platinum, regular plugs and iridium plugs. Still gets to point it does this no matter what type plug you use, but SOMETHING must be causing this to happen. Could voltage regulator be causing spikes that destroy the plugs? Tonight I noticed that with the plugs plugged in outside the cylinder, when I crank it they spark real bright when I first hit start button but then fire real faint untill button is released at which time they fire real bright again. I can turn ignition off and on with key (off/on switch in "on" position) and it sparks real bright each time its turn on and again when turned back off. It appears that it fires with the intensity I would expect only when making or breaking but when firing while trying to start is way less intense. Oh, and the battery is measuring 12.5 volts (is usually 12.8 but I had been cranking quite a bit working on starter) Any help would be greatly appreciated.
Tourer
Joined: Nov 2005
Posts: 282
Likes: 0
From: Georgia
RE: ignition question
You gave us alot of good info and the way I understand it, the problem followed the plug, correct? The one thing that would help even more is whether you still have points or you changed to electrical ignition, (if so, what brand).
(Take this with a grain of salt because my understanding of the electrical is just above intermediate, I can read a meter and can follow a diagram with good troubleshooting skills easily enough but my knowledge of how each of the componants themselves work is novice at best.)
The problem following the plugs may just be coincidence as to where in the rotation the cam loabs are and which plug trys to fire first.
Assuming you have points, I'm going to say replace the condenser. It's my understanding that this is to store and maintain a constant voltage. It's a cheep starting point. Also check the condition of your points. They are mechanical and do wear out. Also check the point gap, which will change due to wear. Check to see if the spark at the points does the same thing that it does at the plugs. I think this would be further indication that the condenser has had it.
If you have electriconic ignition, get in touch with the manufacturers tech support. Often they can steer you in the right direction, even if the problem is not their equipment.
By the way, if you opt to replace the whole points system, don't cheep out and go for the $15 version. I'ts worth the extra cash to get good componants/construction.
I invite others to correct me where I'm wrong, please.
Rich
(Take this with a grain of salt because my understanding of the electrical is just above intermediate, I can read a meter and can follow a diagram with good troubleshooting skills easily enough but my knowledge of how each of the componants themselves work is novice at best.)
The problem following the plugs may just be coincidence as to where in the rotation the cam loabs are and which plug trys to fire first.
Assuming you have points, I'm going to say replace the condenser. It's my understanding that this is to store and maintain a constant voltage. It's a cheep starting point. Also check the condition of your points. They are mechanical and do wear out. Also check the point gap, which will change due to wear. Check to see if the spark at the points does the same thing that it does at the plugs. I think this would be further indication that the condenser has had it.
If you have electriconic ignition, get in touch with the manufacturers tech support. Often they can steer you in the right direction, even if the problem is not their equipment.
By the way, if you opt to replace the whole points system, don't cheep out and go for the $15 version. I'ts worth the extra cash to get good componants/construction.
I invite others to correct me where I'm wrong, please.
Rich
Road Master
Joined: Jun 2006
Posts: 905
Likes: 206
From: Minneapolis
RE: ignition question
we'll need more info
how quickly does the spark burn out....right away....2 weeks???
is it the same coil/spark wire that burns the spark? if yes, you may want to replace the coil.
your coil resistance should be about 4.8 ohms at the dist and points connectors.
if you have points, I doubt it's the condensor, this keeps the points from arcing and burning
does the plug look fouled/oily or burnt? in other words, are you sure this is not a mechanical problem with your top end....
keep in mind that a points system is very simple....battery to coil---points to ground the primary of the coil, plug wires, and plugs that ground to the block (instead of the points when they open)....the whole system costs about 100 bucks new so you can always just start replacin stuff
your weak spark is most likely due to the drain of the starter motor on the battery
how quickly does the spark burn out....right away....2 weeks???
is it the same coil/spark wire that burns the spark? if yes, you may want to replace the coil.
your coil resistance should be about 4.8 ohms at the dist and points connectors.
if you have points, I doubt it's the condensor, this keeps the points from arcing and burning
does the plug look fouled/oily or burnt? in other words, are you sure this is not a mechanical problem with your top end....
keep in mind that a points system is very simple....battery to coil---points to ground the primary of the coil, plug wires, and plugs that ground to the block (instead of the points when they open)....the whole system costs about 100 bucks new so you can always just start replacin stuff
your weak spark is most likely due to the drain of the starter motor on the battery
Road Master
Joined: Mar 2008
Posts: 1,069
Likes: 27
From: Iowa
RE: ignition question
Those other two guys don't seem to know that 1979 was the first full year for Harleys first try at an electronic ignition. They started using it in mid 1978.
They kept the old spring and weight activated timing advance though.
Also you can't use just any old plug wires. The original plug wires were marked withasmallletter H up and downthe outside ofthe plug wire jacket.
Is this the kind of ignition system that's on your bike?
They kept the old spring and weight activated timing advance though.
Also you can't use just any old plug wires. The original plug wires were marked withasmallletter H up and downthe outside ofthe plug wire jacket.
Is this the kind of ignition system that's on your bike?
Thread Starter
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Cruiser
Joined: Jan 2008
Posts: 161
Likes: 1
RE: ignition question
Thanks guys. To answer a couple of the questions, yes the bike has the electronic ignition that came on it in 79, but does not have the original plug wires (has a 5 gallon FLT gas tank and the originals would arc to the tank since the wire was right up against it) Forget what bike I bought plug wiresfor, but they had 90 degree coil ends instead of straight. It seems to go about 2 weeks of riding every day before it does this. Last time the rear plug did this, this time it was the front. Since this has been happening, I've been checking plugs every other day and they always seem light tan in color. I've been working on starter lately so have been starting bike and letting it run a little-repeatedly. This time the plugs were a dry black sooty color but expected that since its been idling alot lately. Was actually riding it after working on starter and adjusting clutch when I was almost home and it started doing it again. Like I said, the last time it did this was a couple of weeks ago.
When I first pulled the plugs and plugged them in outside the cylinder (wedged them between cylinder and horn) and cranked bike, the front would not fire. Swapped front to rear and vice-versa and that same plug still wouldnt fire. After cranking it over a couple of times, it finally started firing both plugs, but just seems real weak. Doesnt fie from electrode to the stem, but instead is firing from electrode to side. Only fires from electrode to stem when turning on and off.
When I first pulled the plugs and plugged them in outside the cylinder (wedged them between cylinder and horn) and cranked bike, the front would not fire. Swapped front to rear and vice-versa and that same plug still wouldnt fire. After cranking it over a couple of times, it finally started firing both plugs, but just seems real weak. Doesnt fie from electrode to the stem, but instead is firing from electrode to side. Only fires from electrode to stem when turning on and off.
Tourer
Joined: Nov 2005
Posts: 282
Likes: 0
From: Georgia
RE: ignition question
ORIGINAL: eglideic
Those other two guys don't seem to know that 1979 was the first full year for Harleys first try at an electronic ignition. They started using it in mid 1978.
Those other two guys don't seem to know that 1979 was the first full year for Harleys first try at an electronic ignition. They started using it in mid 1978.
Wish I could help further and hope you get it figured out soon. Let us know what you find.
Rich
Tourer
Joined: Oct 2007
Posts: 269
Likes: 0
From:
RE: ignition question
I was having a similar issue with my 78. Measured the coil resistance and that was my problem. Replaced the coil and issue was fixed.
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Cruiser
Joined: Jan 2008
Posts: 161
Likes: 1
RE: ignition question
Mine has a new coil, wires and plugs. New circuit breakers, wiring harness, battery, starter reley, starter solenoid, springs, pins, boots etc. Been kinda going through it and trying to replace parts with new as much as I can.
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