Coil Mod - should I do it?

[Steve]

Steve-very much respect your opinion as I've read a lot of your replies to other posts...I tested with engine off / ignition switch on only exactly as per Wired George site instructions. Are you saying that is incorrect? That I should test volts to coils with bike running?

Personally, yes, I would test with the engine running. Isn't that when low voltage would be a problem? The least you could do is to compare what you see at the coils with what you see at the battery under the same conditions. With the headlight on and the coils drawing power, your battery is already under about a 10-amp load. Depending on the condition of the battery, it might only drop a volt or it might be several volts. By the way, I have not seen Wired George's instructions, so I don't know what they are. By the way, you want a REAL eye-opener? Watch the voltage at the coils when you hit the starter button.. THAT is when coil voltage is critical.

I'm gonna go out a limb here and disagree with your disagreement of Lucabond's comment. If there is some thing, anything, within stock wiring that is causing an undue "draw"/"tax" on my charging sys causing my overall numbers (i.e. 12.6 @idle, 13.2v @2000rpm vs. 13.5 @ idle which is ideal per Stator Papers), then surely anything that draws power through the stock harness could be contributing to this. Including headlight and possibly coils too. Unless what you saying is that the sensing circuit in RR should compensate? I am therefore thinking that the coils and headlight relay mods are worth my time since those are "on" / sapping at all times. The horn it seems to me doesn't make much sense since it is only a "draw" when you actually push the horn button (which on my bike is almost never).

Let the "discussion" continue (while I get busy working)....why they call if a "forum" I suppose

OK, now I'm going to disagree with your disagreement of my disagreement.

Allow me to explain. The headlight has a filament with a fixed resistance, so is going to allow a certain amount of current to flow through it. Nothing changes that for any given headlight. If there are some dirty connectors in the supply line or grounding circuit for that headlight, they are going to see the same amount of current. The crud in those connections are going to have some resistance, so will rob some of the voltage from the headlight. Ohm's law says that in a closed circuit, all voltage rises will be matched by the voltage losses, the current remains the same. If you feed the headlight with a different circuit with fewer, cleaner connections (the headlight relay mod), the headlight will still have the same amount of current flowing through it, but it will see more voltage because nothing has been hampering the current flow. As far as the battery is concerned, the headlight will draw the same current with either circuit.

The charging circuit is completely separate. The stator is excited by the magnets in the rotor and puts out some current. That current goes to the rectifier and regulator, then to the battery. Since the battery can't tell whether the headlight is drawing its current through wires with dirty connections or clean ones, it is providing the same current. Because it is providing the same current to the bike, the charging is unaffected. Oh, and the stock R/Rs didn't have a sense wire, so you can't count on that in the original configuration.

What will be affected by these mods is the voltage available at the various devices. Yes, I am familiar with the concept of heavy draw through small wires drawing down the voltage. That is why it helps so much to put in better wires when you do the mod. But it all comes back to Ohm's law, the current will remain the same, but since there are fewer voltage drops due to unwanted resistance, there is more voltage for the intended load.

Does this make sense? :-k

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[KiwiGS]

Ok I agree the general point of what Steve has said, but be careful with how you think of a lamps resistance; they are not ohmic so they do not have a fixed resistance. The resistance changes as the filament gets hot.
So
snip<"The headlight has a filament with a fixed resistance, so is going to allow a certain amount of current to flow through it. Nothing changes that for any given headlight">snip
is not quite true.
Other than that what he says...

 

[Steve]

Ok I agree the general point of what Steve has said, but be careful with how you think of a lamps resistance; they are not ohmic so they do not have a fixed resistance. The resistance changes as the filament gets hot....

You are very correct, but I was just trying to minimize the variables and keep it in simple terms for the layman.

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[lucabond]

It just seems to me if the bike's electrical system was made for load X and due to the old wiring and connectors the load is now load X plus then the system will not work as designed. No amount of cleaning will get some of these old harness's back into shape. WE already connect the RR's directly to the battery due to the losses in the original wiring same for the coils via the coil mod the other big draw is the headlight. I power my headlight and most of the dash lights via a coil. After doing the mod I noticed a marked improvement in the brightness of all. Taking this load off the old harness has also made my blinkers and tail light much brighter even though I didn't change the way they were powered. I have had a couple people tell me they thought my brake light was staying on until I hit the brakes they couldn't believe how bright it was. Just for kicks you could run a jumper direct from the battery to the headlight, see if the brightness increases then see what the voltage does at the battery at idle and 5k.Good luck

 

[tkent02]

Allow me to explain. The headlight has a filament with a fixed resistance, so is going to allow a certain amount of current to flow through it. Nothing changes that for any given headlight. If there are some dirty connectors in the supply line or grounding circuit for that headlight, they are going to see the same amount of current.

Except if you add resistance in series with the bulb, such as a few corroded connectors here and there, you reduce the current, which reduces the voltage drop at the bulb. Voltage drops at each corroded connector add up, the total remains the same.

All the voltage drops add up to equal the system voltage, no?

 

[Steve]

Except if you add resistance in series with the bulb, such as a few corroded connectors here and there, you reduce the current, which reduces the voltage drop at the bulb. Voltage drops at each corroded connector add up, the total remains the same.

All the voltage drops add up to equal the system voltage, no?

True, the voltage gains (battery supply) will equal the voltage drops (lights, coils, corroded connections, etc.), but the current doesn't really change that much due to the corroded connectors unless they are REALLY corroded. They are simply another voltage drop because of their resistance. Because you are dropping some voltage at the connectors, there is less voltage available at the light. The total current for that circuit will remain pretty much constant.

Nessism has it right, ... "to measure is to know".
Anybody have a badly corroded system that can measure the current draw, then do a relay mod and compare the current? :-k

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[Speedo]

Steve (et al please chime in) - so I try to run the volts test on the coil with bike running today and I can't get a reading. The meter is all over the place and when I tried to "dig" the probe into the coil +pos terminal, I got a bunch of sparking which had no effect on the bike running (but scared the sh*t out of me). BTW, for "control" test, I tested coils w bike off (as before) and got the same or close readings as before. Used same engine bolt as ground for both tests. Bad meter? Wtf am I doing wrong? Maddening.

Anyway, no coil mod prob this weekend since Shirazdrum is coming and will be spending night tomorrow. Went out today and no relay pigtail at other 2 local auto parts stores. Double arggghh. NAPA is only store left to check.

Trying to get the dang bike together to ride with Shirazdrum tomorrow and literally had a 4 wire plastic connector in the headlamp crumble in my hands an hour or so ago. Arggghhh. So now I gotta redo that whole mess in the morning.

THEN....go to pull car out of garage and it has dead battery (which is brand new less than a month ago so I just KNOW I got another problem there), so I can't move car out, and bike in to work on/put back together tonight since my shed has no electric and garage does, and not to mention as well as my intention of creating a parking spot for Shirazdrum tomorrow night )....TRIPLE arggghhh

How do mechanics "deal" from day to day?

 

[Steve]

Steve (et al please chime in) - so I try to run the volts test on the coil with bike running today and I can't get a reading. The meter is all over the place and when I tried to "dig" the probe into the coil +pos terminal, I got a bunch of sparking which had no effect on the bike running (but scared the sh*t out of me). BTW, for "control" test, I tested coils w bike off (as before) and got the same or close readings as before. Used same engine bolt as ground for both tests. Bad meter? Wtf am I doing wrong? Maddening.

Not sure why you would have gotten any sparks, there should only be 10-14 volts there. One suggestion would be to use the battery for your ground, not an engine bolt. Using a bolt for a ground, you are relying on a good, corrosion-free connection between the bolt and the engine, then another connection from the engine to a ground wire, then another connection from the ground wire to the battery. Try to troubleshoot with as few unknowns as possible.

Went out today and no relay pigtail at other 2 local auto parts stores. Double arggghh. NAPA is only store left to check.

No need for a pigtail, just use insulated female spade connectors. If you can't find insulated connectors, use regular ones, but cover them with shrink wrap. Using a pigtail might sound like a good idea, but you are going to have to extend those wires to reach whatever it is you are trying to power with it, and there are more connections involved. If you solder those connections to prevent corrosion, that's OK, otherwise, you are just introducing more points to have corrosion.

Trying to get the dang bike together to ride with Shirazdrum tomorrow and literally had a 4 wire plastic connector in the headlamp crumble in my hands an hour or so ago. Arggghhh. So now I gotta redo that whole mess in the morning.

For a temporary repair for your ride, separate the four wires, wrap them in electrical tape. For a more permanent repair, look for new connectors at Vintage Connections or CRC2.

How do mechanics "deal" from day to day?

Not sure. Maybe they have a higher tolerance for that kind of stuff or they simply amuse themselved differently.
For the rest of us who are not mechanics, we tend to follow the advice that BassCliff posts in his Mega-Welcome:
Start at the headlight, check and clean EVERY connection between the headlight and tail light.By doing it all at one time you will assure yourself that everything is OK and you will find problems like crumbling connectors.

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[willie]

I installed a coil relay in my '79GS550 a couple of weeks ago. It was the 3rd GS I've done the coil relay on but my 1st with points ignition. I was surprised at how fine gauge the coil wires were. No wonder they don't get much current after a few decades. I was impressed with the overall improvement after modifying my 1100s but was really blown away by the difference in the performance of the 550 with the coil relay. Starts are, without a doubt, the quickest I've xperienced on ANY bike. I've attached a pic of the relay and fuse holder I used for ease in finding one at the auto parts store. I bought mine at O'Reily's.
Willie

 

[Speedo]

Shirazdrum has been here last 2 nights thankfully, he's a bit of an electrical genius, and thankfully also, even though we were supposed to be wrenching on HIS bike, he was happy to spend 80% of our wrenching time on MY bike -all while subjecting him to country music while wrenching.
What a great guy and great cause!

Anyway, turns out at least one definite problem all along has been the RR going bad and not working but INTERMITTANTLY (think light bulb going bad and flickering until dead). Extreme voltage spikes was causing the mysterious bike running good one day, bad the next, "healing itself" and running good again for no apparent reason, along with coils not getting proper voltage, along with plugs getting fouled in the process even though they had less than 200mi on them.

... last post...including BassCliff told me read the Stator Papers and test my charging system. Prev thread below where bike drained battery and ran like crap and apparently "healed" itself.

http://www.thegsresources.com/_forum...ight=runs+crap

However, noone really has answered the question: can a drained battery alone cause the bike to run terrible (w/ Dyna S, etc)??

ANSWER: NOPE. BUT TOASTED RR SURE CAN! MORE...

... all over 60, but it the readings were not "rock solid" and fluctuated occasionally - don't know if that matters; if so, how else to test?)

ANSWER: OH YEAH IT MATTERS:!: Fluctuation is a BAD sign...readings should be virtually rock solid. If your readings are jumping around, suspect the RR. Shiraz showed my on his GS850 how the reading should look a bike with everything working properly which was "worth a 1000 words".

What finally solved it (thank you Shirazdrum - you ARE "the man"), was
1. Disconnect RR which take both RR and Stator out of spark loop.
2. Fully charge battery (make sure it's good)
3. Do coil mod to make sure coils getting full 12v and spark is good
4. Fresh plug (just to make SURE plugs are not contributing to problem).