Warm coils

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Dave Edmunds

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Jan 31, 2009
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I have a '70 Norton custom that I purchased a while ago that is having starting problems. I am getting spark but it will not start. It has a point system and the wires going to the coils have been split and are connected to the positive terminals of the coils. I have just noticed that the coils are both warm to the touch and wondered if this is normal. (I never noticed this before). The bike ran before I replaced the head gasket and removed all of the coil wires. Now I'm reassembling and it will not start. Any help would be appreciated.

Thanks
 
Dave Edmunds said:
It has a point system and the wires going to the coils have been split and are connected to the positive terminals of the coils.
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Has your Commando been converted to negative earth/ground polarity? If not, then the main (white) power wire should be going to both coil negative terminals? Each positive coil terminal should connect to one points wire and a condenser/capacitor.
 
It is a positive ground system and the white wires are connected to the negative poles of the coils. I have good spark but I am wondering if the coils should be warm or if this is a sign of something wrong?
 
Have you checked that the push rods have seated properly and that you have compression? Also try squirting some raw fuel into the carb mouths. If you have fuel, compression and a spark you should get at least some kind of combustion. Coils do get warm when you pass current through them, although with a points set-up I would expect only one to get warm with the ignition left on, this would correspond with the one set of points in the closed position.
 
Thanks for the ideas, there is good compression. I was really concerned that there was something wrong with the coils being warm. I will try the raw fuel idea tomorrow.
 
Standard Lucus wiring with key left on will allow current to flow through coils so they can get really hot if long and battery enough. Its really easy to get the points
mixed up d/t the both pistons up at once and piston rise valves open or closed will give a puff out the plug hole to fool ya on which in on compression, ugh.
Recheck timing, again, as I've had to before shooting me or bike.

Power to coils in Lucas set up should go to the ballast restior pack then to coils. Condensors are on ballast mount and I've had them go bad to give a spark but not protect from arching enough to pump coil up to fire in compression.
 
Hobot brings up a good point, do make sure that you haven't inadvertently connected the right points wire to the left coil etc.
 
hobot said:
Standard Lucus wiring with key left on will allow current to flow through coils so they can get really hot if long and battery enough. Its really easy to get the points
mixed up d/t the both pistons up at once and piston rise valves open or closed will give a puff out the plug hole to fool ya on which in on compression, ugh.
Recheck timing, again, as I've had to before shooting me or bike.

Power to coils in Lucas set up should go to the ballast restior pack then to coils. Condensors are on ballast mount and I've had them go bad to give a spark but not protect from arching enough to pump coil up to fire in compression.
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1968-1970 originally used 12v coils and NO ballast resistor


1971to the end were 6V w/ballast.
I suspect for the failed starter mod.... starting in 1971 and just never bothered to revert back to 12v
 
I've always wondered why they went to the ballast and the 6V coils. My 69 has just the points, 12V coils and no ballast. Seems to work just fine for me. Doesn't have the wasted spark either, just fires when needed. Seems very simple to me, but then I'm pretty much of a Luddite.

Dave
69S
 
If you like Luddites, check out Antipodeans.

Dave
69S
 
Here is another idea for warm coils , the coil clamp bolts torque reading is 2 lbs. Yes two lbs., less than the force it takes to pick a booger out of...the clamps if overtightened will crush the alluminium body of the coil to its own internal windings causing problems. Substitution with known good is how I isolate confusing electrical probs. You can easily see "crushing" if it has occurred.
 
Dave Edmunds said:
I have a '70 Norton custom that I purchased a while ago that is having starting problems. I am getting spark but it will not start. It has a point system and the wires going to the coils have been split and are connected to the positive terminals of the coils. I have just noticed that the coils are both warm to the touch and wondered if this is normal. (I never noticed this before). The bike ran before I replaced the head gasket and removed all of the coil wires. Now I'm reassembling and it will not start. Any help would be appreciated.

Thanks
Click to expand...

The coils will get hot sepecially if you leave ignition on for any period of time because one set of points will be closed hence current flow through the coil affected you can checkit out by turning over the engine so that each set of point is closed then check coils after 10 minutes one will be hotter the other will not. Hence never just leave the ignition on for ages with bike stationary.
 
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