burnt ground wire

so i got that shit all sorted out, i still can't get it to pop. last night i managed to leave the key is the first position, came out today and baby the right coil was hot. I still have spark, and i know i setup the points properly. I hope i didn't damage anything. Good thing my battery tender was hooked up.

The only thing that hasn't made any sense when setting up the points was using a bulb connected from the points spring to the cylinder head. I've read that in many posts and in the shop manual too. The thing is, there is the same potential at both spots, both being positive ground. How is a bulb going to light up? I just ran a clip back to ground on the battery to the points spring. Same thing? Either way i managed to statically set em up using the bulb @28degrees, full advanced. I'll tune em with a light when i can get the damn thing to start.

In the mean time i'm waiting for another petcock sealing washer since the other one failed to seal. Kept dripping and then fell apart when i took it off. Yes it's the bonded type. So things are on hold till i can put the tank back on.

L.A.B. said:

NoHoNorton said:

I am still curious why that wire got hot and smoked.

Snipping it may SEEM to have cured the problem but I suggest using an ammeter inits place and see what kind of current is flowing. I predict a lot.

The next question is why is all this current charging along this route?

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I believe I have already given the reason here why this occurs.

= If the heavy gauge positive ground battery wire is not making proper electrical contact either at the engine or battery because something has loosened, corroded or is not fitted correctly, the starter current re-routes through any harness ground wire that happens to be connected to the battery ground (in this case = positive) terminal when the starter is operated.

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Apologies, Les. Goes to show that skimming through posts late at night is not a good idea. :?

GavinJuice said:

so i got that shit all sorted out, i still can't get it to pop. last night i managed to leave the key is the first position, came out today and baby the right coil was hot. I still have spark, and i know i setup the points properly. I hope i didn't damage anything. Good thing my battery tender was hooked up.

Click to expand...

Correct me if I am wrong but the Commando is a parallel twin so both sparkies fire together and also the coils are in series.

So Gavin, if only the right coil was hot I would assume the left coil is shot, shorted it would seem.

My reasoning is that you left the ignition on, the points were closed, current flowed through points into coils, coils would then get warm except it seems the left coil did not so it must have been passing the current direct to ground.

If one coil is shorted you will be getting a pretty uneven/weak spark methinks.

Hope this helps.

"Correct me if I am wrong" Right info for a boyer equipped Norton but not for a points bike. With ing. on only one or none of the coils will get hot depending on your luck. Go back and read a mark 3 with points that was my Dad's bike.

I agree with norbsa, if the engine is not running but the ignition has been left switched on for long periods then the coil that happens to have its points set closed at the time will be constantly grounded/earthed, and the coil will heat up as a result, which doesn't really do it much good.

(Boyer ignition systems switch off electronically after a certain number of seconds if the box doesn't sense any pulses from the pickup.)

Let it cool look for oil coming out. See if it still works. There are good stock coils all over the place.

GavinJuice said:

The only thing that hasn't made any sense when setting up the points was using a bulb connected from the points spring to the cylinder head. I've read that in many posts and in the shop manual too. The thing is, there is the same potential at both spots, both being positive ground. How is a bulb going to light up?

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The points spring/s should be negative, not positive polarity, a bulb connected between the spring and ground should light (or become brighter) as the points open if the bike's own ignition circuit is used to set the timing? If you use a separate battery and bulb with the ignition switched off then the opposite should happen, the light goes off as the points begin to open.

Each points spring post and spring securing nut is positive (grounded). Although the points spring pivots on the post it (and its coil wire terminal) should be electrically isolated from it by the insulating washers?

?

Yes the diagram is correct??

But I think you might be misunderstanding it if your intention was to show the points as being 'positive'? (Was that your intention? You do not say?)

As they are shown to be on the *positive side* of the coils....but that doesn't make them *positive* as each component has a *positive* and *negative* side.

__(+battery-)_______(-switch+)____(-ballast resistor+)________(- coil +)________(-points+)________(+Ground)__

Technically, the ballast resistor does not have to be connected a particular way round with regard to polarity and the switch would be connected according to the terminal markings although its actual polarity connection isn't that important, so is why they have no polarity symbols shown on the diagram, and the points can only go one way, the battery and coils however, do need to be connected correctly with regard to polarity as shown in the diagram.

yes i was seeing them as being positive.

L.A.B. said:

I agree with norbsa, if the engine is not running but the ignition has been left switched on for long periods then the coil that happens to have its points set closed at the time will be constantly grounded/earthed, and the coil will heat up as a result, which doesn't really do it much good.

(Boyer ignition systems switch off electronically after a certain number of seconds if the box doesn't sense any pulses from the pickup.)

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I hope I am not taxing everyone's patience but shouldn't both sets of points open and close at the same time or do I have the concept of "parallel twin" wrong?

Both cylinders fire together on the power stroke????

IF that is the case then one set of points being closed and the other open would then suggest the points need resetting.

Then I ask myself if both cylinders fire together why are there two sets of points? (looking at that wiring diagram posted by Gavin)

Why do people talk about the coils being wired in series when this diagram shows them wired in parallel?

My motorbike experience, back in my callow youth, was limited to a 1961 Matchless G80CS 500 cc single so my very recently acquired 1969 Commando S (Boyer ignition) is a mystery, unfolding thanks to the fine folks posting here.

Boyer fires both plugs at the same time, one spark is wasted on an exhaust stroke. One ignition system provides sparks for two cylinders

British twins fitted with Lucas coil ignition have a seperate ignition system for each cylinder and only spark on the compression stroke for that cylinder. The points will not, should not open at the same time.

I'm sure LAB will explain it better he likes letric.

As cash says, the cylinders in a British parallel twin (normally) fire 360 degrees apart = each cylinder fires for one crankshaft revolution, as it takes two crankshaft revs for each cylinder to go through all four strokes (or cycles = US) this design has its big ends in line with each other and this gives a regular power stroke every rev in a 4 stroke parallel twin engine.

Some four stroke parallel twins (many Japanese twins) have 180 degree cranks, the big ends being 180 degrees apart so the power strokes are not as regular and there are pros and cons for both types which I will not go into here as the question was about points opening, and each set of points opens once for every two crankshaft revolutions, as the camshaft that drives the AA unit operates at half crank speed; 360 crank degrees = 180 camshaft & points cam degrees, therefore one points set should open every 180 degrees of camshaft rotation. Two stroke parallel twins normally have 180 deg. cranks as a 2S twin will fire every 180 deg. their points and points cam are generally mounted on the crankshaft so produce sparks 180 deg. apart.

Each points set needs to be set independently of the other, so they open at the correct firing point for their particular cylinder (28 deg. BTDC fully advanced for Commandos), and it is when the points open that the spark occurs (and not when they close which may appear more logical to anyone not understanding how the ignition spark is generated).

Some types of 360 degree parallel twins use only one set of points with a double wire coil to supply a spark to both cylinders at the same point by opening the points twice each camshaft revolution = once every crank rev as there are two cam lobes 180 deg. apart on the AA unit, this system is normally referred to as a *wasted spark* system, as only one of the two sparks produced fires whichever cylinder is on the compression stroke, the other spark is wasted as the other cylinder will be on its exhaust stroke.

The wasted spark system is also how most electronic ignition systems operate (not the Tri-Spark type) by supplying a spark to both cylinders every 360 degrees of crankshaft rotation.

NoHoNorton wrote:

Both cylinders fire together on the power stroke????

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Then I ask myself if both cylinders fire together why are there two sets of points?

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If I understand what you mean, you think that both pistons are on power stroke together, whereas the power stroke is alternated on the parallel twins, so that every time the pistons reach top dead centre, one cylinder is on compression/power, the other is on exhaust/induction.

Hence as cash wrote

British twins fitted with Lucas coil ignition have a seperate ignition system for each cylinder and only spark on the compression stroke for that cylinder. The points will not, should not open at the same time.

Click to expand...

Boyer fires both plugs at the same time, one spark is wasted on an exhaust stroke.

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Oh dear, I see that whilst I was typing this, LAB has composed a much more comprehensive reply. Sorry, didn't mean to double up on the reply.

I thank you all.

Les, I had a total misconception on the parallel twin.

I did indeed, Reggie, think that both cylinders were power stroking at the same time.

Cheers,

Steve