My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same. The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric

On 6/4/2014 8:15 PM, wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same. The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric

Rl is the time constant. Likely the heat of the spark in one cylinder
is needed to be more or less.
Timing is critical and heat is also.

Martin

wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same. The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric

Yup, the coils need to have the same resistance. Your son is correct in
the reason the timing is off.


--
Steve W.

On Wed, 04 Jun 2014 23:27:31 -0400, "Steve W."
wrote:

wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same. The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric

Yup, the coils need to have the same resistance. Your son is correct in
the reason the timing is off.
When he says the timing is off, how is it being determined and how
far off is the timing? If he is checking with a timing light on the
secondary it might be BAREL:Y noticeable but the coils should be
matched for other reasons. The build-up has nothing to do with timing
- the spark happens when the magnetic feild collapses.(unless it is a
capacitive discharge system -which is a totally different kettle of
fish)

On Wednesday, June 4, 2014 9:15:55 PM UTC-4, wrote:
My son was wondering

if the difference in timing could be because one coil takes longer to

build up enough voltage to cause the spark plug to spark.

Eric


I doubt it. Assuming this is a Kettering type of ignicion, the way it works is that when the points are closed the current builds up in the coil. When the points open the magnetic field collapses which creates the high voltage. The condenser across the points keeps the voltage from arcing at the points. You might swap the condensers and see if that changes things. If it does one of the condensers is bad.

Dan

On 6/4/2014 9:15 PM, wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same. The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric


Chances are that the two coils were the same at one time.

On Thu, 5 Jun 2014 04:05:12 -0700 (PDT), "
wrote:

On Wednesday, June 4, 2014 9:15:55 PM UTC-4, wrote:
My son was wondering

if the difference in timing could be because one coil takes longer to

build up enough voltage to cause the spark plug to spark.

Eric


I doubt it. Assuming this is a Kettering type of ignicion, the way it works is that when the points are closed the current builds up in the coil. When the points open the magnetic field collapses which creates the high voltage. The condenser across the points keeps the voltage from arcing at the points. You might swap the condensers and see if that changes things. If it does one of the condensers is bad.

Dan
Greetings All,
I guess it's sort of a Kettering ignition. It doesn't use points
though. Some type of inductive sensor tells a box when to make the
coils spark. My son says he checked the timing with a timing light,
which is why he knows when each coil is firing.
Eric

On Thu, 05 Jun 2014 09:11:06 -0700, wrote:

On Thu, 5 Jun 2014 04:05:12 -0700 (PDT), "
wrote:

On Wednesday, June 4, 2014 9:15:55 PM UTC-4, wrote:
My son was wondering

if the difference in timing could be because one coil takes longer to

build up enough voltage to cause the spark plug to spark.

Eric


I doubt it. Assuming this is a Kettering type of ignicion, the way it works is that when the points are closed the current builds up in the coil. When the points open the magnetic field collapses which creates the high voltage. The condenser across the points keeps the voltage from arcing at the points. You might swap the condensers and see if that changes things. If it does one of the condensers is bad.

Dan
Greetings All,
I guess it's sort of a Kettering ignition. It doesn't use points
though. Some type of inductive sensor tells a box when to make the
coils spark. My son says he checked the timing with a timing light,
which is why he knows when each coil is firing.
Eric
====================
two types of ignitions

Kettering, where the coil "fires" when the points open.
This is because the magnetic field in the coil collapses
faster than it builds giving a "hotter" spark.

CD [capacter discharge] where a capacter discharges a higher
surge of current/voltage with a faster rise time into the
coil and it fires as the magnetic field builds up. If you
have a "pointless" system, which is likely as you mention a
module rather than points, it may well be a CD. Is this a
computerized system where the advance is controlled by the
module, and the sensor or points are just index location
signals?

Coils are not that expensive, and he should use a matched
set of used coils, if not new a new set.

here's a few places to start

http://www.motorcycle-superstore.com...gnition%20Coil

http://ricksmotorsportelectrics.com/ignition-coils

http://www.jcwhitney.com/ignition-sw...1121j1s17.jcwx


--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"

Dan sez:

The condenser across the points keeps the voltage from arcing at the
points. You might swap the condensers and see if that changes things.
If it does one of the condensers is bad.

We stopped using the term "condenser" in the 1960s G

ANYway... that's not all the capacitor does. It also controls the decay
time of the field in the coil. And that depends upon the inductance of
the coil -- the old "LC constant".

If the coils are noticably different in resistance, there's a really good
chance they have pretty large differences in numbers of turns. That
vastly affects the inductance of the coil.

If you wish to have both coils "fire" at the same time, you must have
them inductively matched, and have the same capacitance across both sets
of points (gotta be two, unless they were really dolts and paralleled two
coils!)

Don't forget point gap. If there are two sets, then if they're not
gapped exactly the same, the timing will change there, too.

Two new coils, two new capacitors, and two new sets of points are the
best way to go. (might as well throw in plugs and HT wires, too...)

LLoyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

(gotta be two, unless they were really dolts and paralleled two
coils!)

That's on the assumption that both coils fire at the same time, but of
course, if they don't then why are there two coils?

Lloyd

"F. George McDuffee" wrote in
message ...
On Thu, 05 Jun 2014 09:11:06 -0700, wrote:

two types of ignitions

Kettering, where the coil "fires" when the points open.
This is because the magnetic field in the coil collapses
faster than it builds giving a "hotter" spark.

CD [capacter discharge] where a capacter discharges a higher
surge of current/voltage with a faster rise time into the
coil and it fires as the magnetic field builds up. If you
have a "pointless" system, which is likely as you mention a
module rather than points, it may well be a CD. Is this a
computerized system where the advance is controlled by the
module, and the sensor or points are just index location
signals?


My truck's electronic ignition is somewhat like a motorcycle's, with
one coil firing two plugs on every crank revolution, one before
compression TDC and the other before exhaust TDC.
http://rockledge.home.comcast.net/~r...y/DIS_EDIS.htm
"The spark plug on the compression stroke uses the majority of the
coil's stored energy, while the other spark plug, on its exhaust
stroke, uses very little of that energy."

The ignition module acts like points and fires by interrupting the
coil current.
"When the switch opens, the power is interrupted and the primary field
collapses, inducing high voltage pulses into the secondary coil
windings."

-jsw

"Jim Wilkins" fired this volley in news:lmqq4k$leh$1
@dont-email.me:

"When the switch opens, the power is interrupted and the primary field
collapses, inducing high voltage pulses into the secondary coil
windings."


No! Really?
(C'mon, Jim...)
Lloyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this
volley in
. 3.70:

(gotta be two, unless they were really dolts and paralleled two
coils!)

That's on the assumption that both coils fire at the same time, but
of
course, if they don't then why are there two coils?

Lloyd

On my truck there are two independent sets of coils and plugs, on
opposite sides of the engine. Except during starting they fire at the
same times. I could add a Mag Drop switch.

-jsw

"Jim Wilkins" fired this volley in news:lmqqta$q4t$1
@dont-email.me:

On my truck there are two independent sets of coils and plugs, on
opposite sides of the engine

And points, no? If only one set of points, it's a system destined to be
unreliable. Even minor changes can affect the timing and voltage of the
spark on one coil.

Lloyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Jim Wilkins" fired this volley in
news:lmqq4k$leh$1
@dont-email.me:

"When the switch opens, the power is interrupted and the primary
field
collapses, inducing high voltage pulses into the secondary coil
windings."


No! Really?
(C'mon, Jim...)
Lloyd

Really, Lloyd!

I've got an ignition module open here. The coil driver "switches" are
5mm square MOSFETs (comb-like gate pattern) on a ceramic hybrid
substrate, with something that might be the voltage clamp to ground
next to each. It's potted in clear silicone which I won't disturb just
to answer you.

-jsw

On Thu, 05 Jun 2014 16:13:46 -0500, F. George McDuffee
wrote:

On Thu, 05 Jun 2014 09:11:06 -0700, wrote:

On Thu, 5 Jun 2014 04:05:12 -0700 (PDT), "
wrote:

On Wednesday, June 4, 2014 9:15:55 PM UTC-4, wrote:
My son was wondering

if the difference in timing could be because one coil takes longer to

build up enough voltage to cause the spark plug to spark.

Eric


I doubt it. Assuming this is a Kettering type of ignicion, the way it works is that when the points are closed the current builds up in the coil. When the points open the magnetic field collapses which creates the high voltage. The condenser across the points keeps the voltage from arcing at the points. You might swap the condensers and see if that changes things. If it does one of the condensers is bad.

Dan
Greetings All,
I guess it's sort of a Kettering ignition. It doesn't use points
though. Some type of inductive sensor tells a box when to make the
coils spark. My son says he checked the timing with a timing light,
which is why he knows when each coil is firing.
Eric
====================
two types of ignitions

Kettering, where the coil "fires" when the points open.
This is because the magnetic field in the coil collapses
faster than it builds giving a "hotter" spark.

CD [capacter discharge] where a capacter discharges a higher
surge of current/voltage with a faster rise time into the
coil and it fires as the magnetic field builds up. If you
have a "pointless" system, which is likely as you mention a
module rather than points, it may well be a CD. Is this a
computerized system where the advance is controlled by the
module, and the sensor or points are just index location
signals?

Coils are not that expensive, and he should use a matched
set of used coils, if not new a new set.

here's a few places to start

http://www.motorcycle-superstore.com...gnition%20Coil

http://ricksmotorsportelectrics.com/ignition-coils

http://www.jcwhitney.com/ignition-sw...1121j1s17.jcwx
Greetings George,
The ignition is not a capacter(sic) discharge system. It has some sort
of electronics package that controls the ignition timing and uses a
transistor to switch the coil power. So the coil does get the high
voltage from a collapsing field. As regards the need for matched coils
you are right, he should be using the correct matched coils. I have
told him this. He continues to half ass the work on this bike and I
continue to give him **** for it. But his question got me wondering so
that's why I posted it here.
Eric

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Jim Wilkins" fired this volley in
news:lmqqta$q4t$1
@dont-email.me:

On my truck there are two independent sets of coils and plugs, on
opposite sides of the engine

And points, no? If only one set of points, it's a system destined
to be
unreliable. Even minor changes can affect the timing and voltage of
the
spark on one coil.

Lloyd

http://rockledge.home.comcast.net/~r...y/DIS_EDIS.htm
Look at figure 2. SPOUT is Spark Out, a logic signal which mimics the
closing and opening times of points for the correct dwell and timing.
The DIS module connects the (-) sides of the coils to ground like
points, but electronically, and sends back something relevant to how
the coil fired on IDM, Ignition Diagnostic Monitor. IDM was flaky on
the module I replaced, giving a code though the engine ran well
enough.

It's a computer controlled Kettering system, not CDI.

-jsw

"Jim Wilkins" fired this volley in news:lmqv4f$jc3$1
@dont-email.me:

It's a computer controlled Kettering system, not CDI.

It still has two sets of "points", whether they be big MOSFETs or
mechanical.

Lloyd

fired this volley in
:

The ignition is not a capacter(sic) discharge system. It has some sort
of electronics package that controls the ignition timing and uses a
transistor to switch the coil power. So the coil does get the high
voltage from a collapsing field.

"Electronic ignitions" have been around for decades. Simple. They just
replace points with large transistors, and do the sensing of when to fire
magnetically or by a controlled-reluctance coil and reluctor mass.

Lloyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.70...
"Jim Wilkins" fired this volley in
news:lmqv4f$jc3$1
@dont-email.me:

It's a computer controlled Kettering system, not CDI.

It still has two sets of "points", whether they be big MOSFETs or
mechanical.

Lloyd

Actually it has four MOSFET switches, two for the right side coils and
two for the left side coils, two plugs per cylinder. They replace the
point contacts and the computer replaces the distributor point cam and
the centrifugal and vacuum advance.

-jsw

On 6/4/2014 9:15 PM, wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same.

No, it shouldn't. Very few bikes fired both cylinders at the same time.
How many cylinders, what type of bike, what year?



The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric

Steve Walker fired this volley in news:Lrydnd-
:

No, it shouldn't. Very few bikes fired both cylinders at the same time.
How many cylinders, what type of bike, what year?

Of course it should be! We're not talking about both cylinders going TDC
at the same time, we're talking about timing relative to TDC on each. !

Ignition "Timing" has never referred to which cylinder fires when, but when
it fires relative to TDC.

Lloyd

On Thu, 05 Jun 2014 16:54:37 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Dan sez:

The condenser across the points keeps the voltage from arcing at the
points. You might swap the condensers and see if that changes things.
If it does one of the condensers is bad.

We stopped using the term "condenser" in the 1960s G

ANYway... that's not all the capacitor does. It also controls the decay
time of the field in the coil. And that depends upon the inductance of
the coil -- the old "LC constant".

If the coils are noticably different in resistance, there's a really good
chance they have pretty large differences in numbers of turns. That
vastly affects the inductance of the coil.

If you wish to have both coils "fire" at the same time, you must have
them inductively matched, and have the same capacitance across both sets
of points (gotta be two, unless they were really dolts and paralleled two
coils!)

Don't forget point gap. If there are two sets, then if they're not
gapped exactly the same, the timing will change there, too.

Two new coils, two new capacitors, and two new sets of points are the
best way to go. (might as well throw in plugs and HT wires, too...)

LLoyd
Except it has a "controlox" instead of points and condensers - but the
pickups can still be adjusted to set the timing. My STRONG suspicion
is he can put in 2 identical coils (which he SHOULDdo,) and he will
still have a timing issue

On Thu, 5 Jun 2014 18:28:18 -0400, "Jim Wilkins"
wrote:

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.3.70...
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this
volley in
. 3.70:

(gotta be two, unless they were really dolts and paralleled two
coils!)

That's on the assumption that both coils fire at the same time, but
of
course, if they don't then why are there two coils?

Lloyd

On my truck there are two independent sets of coils and plugs, on
opposite sides of the engine. Except during starting they fire at the
same times. I could add a Mag Drop switch.

-jsw

Sounds like a Ford Ranger or a Nissan??

On Thu, 05 Jun 2014 17:46:28 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Jim Wilkins" fired this volley in news:lmqqta$q4t$1
:

On my truck there are two independent sets of coils and plugs, on
opposite sides of the engine

And points, no? If only one set of points, it's a system destined to be
unreliable. Even minor changes can affect the timing and voltage of the
spark on one coil.

Lloyd
Electronic ignition - and computerized timing advance on the only 2 2
plug per cyl automotive/light truck engines I'm aware of.

On Thu, 05 Jun 2014 18:47:25 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

fired this volley in
:

The ignition is not a capacter(sic) discharge system. It has some sort
of electronics package that controls the ignition timing and uses a
transistor to switch the coil power. So the coil does get the high
voltage from a collapsing field.

"Electronic ignitions" have been around for decades. Simple. They just
replace points with large transistors, and do the sensing of when to fire
magnetically or by a controlled-reluctance coil and reluctor mass.

Lloyd
Combined with a digital delay. The spark timing and the pulse on the
position sensor are 2 totally different points in time, with the
actual ignition event timing being calculated by the microcomputer
based on the input from intake air temperature, throttle position
and/or Manifold Absolute Pressure and/or Mass Airflow sensor, plus
coolant temperature sensor, and in some cases a transmission shift
sensor (knowing what gear the engine is in) based on the crankshaft
and/or camshaft sensor (which is not just a single signal at TDC.) In
a lot of cases it's a 42 tooth "gear" with 2 teath missing, which
allows the computer to calculate exactly where the crank is at all
times after as few as 2 complete turns of the crank (1 complete firing
cycle) They are COMPLETELY different than the old "integrated
ignition" and "High Energy Ignition" and "duraspark" systems of old. A
lot closer to Chrysler's old "lean burn" system in concept

fired this volley in
:

Electronic ignition - and computerized timing advance on the only 2 2
plug per cyl automotive/light truck engines I'm aware of.

A lot of them tried it in prototype, and should have stuck with it.

Anyone who's flown knows the difference in power that occurs when you
switch to just one plug. ALL ATC'd aircraft (with piston engines) have
dual ignition circuits. In aircraft, they're totally independent --
absolutely NO common components between the two systems, and often they
are magneto systems to simplify the system, and ensure ignition in the
absense of DC power in the aircraft.

Lloyd

fired this volley in
:

Combined with a digital delay. The spark timing and the pulse on the
position sensor are 2 totally different points in time, with the
actual ignition event timing being calculated by the microcomputer
based on the input from intake air temperature, throttle position
and/or Manifold Absolute Pressure and/or Mass Airflow sensor, plus

Snicker! We're talking about a kid's two-cylinder MOTOSICLE! Not a
friggin CAR!

LLoyd G

On Thu, 05 Jun 2014 10:01:14 -0400, Tom Gardner Mars@Tacks wrote:

On 6/4/2014 9:15 PM, wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same. The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric


Chances are that the two coils were the same at one time.
Likely one is from a point ignition system with no ballast resistor
(nominal 3.5 ohm) or with Ballast resistor (Nominal 1.5 ohm) and the
other is from an electronic ignition unit (nominal .5 or 1 ohm
depending on the system), or one is for with ballast and one without.
On a point system he'd be frying points on the low resistance coil,
while electronic ignition systems "generally" are more "agnostic" when
it comes to coil resistance/current.

On Thu, 05 Jun 2014 20:54:38 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

fired this volley in
:

Electronic ignition - and computerized timing advance on the only 2 2
plug per cyl automotive/light truck engines I'm aware of.

A lot of them tried it in prototype, and should have stuck with it.

Anyone who's flown knows the difference in power that occurs when you
switch to just one plug. ALL ATC'd aircraft (with piston engines) have
dual ignition circuits. In aircraft, they're totally independent --
absolutely NO common components between the two systems, and often they
are magneto systems to simplify the system, and ensure ignition in the
absense of DC power in the aircraft.

Lloyd
2 plug per cyl systems are a requirement on large bore engines to
ensure all of the charge gets lit. On a small bore engine they are not
required, and the ONLY reason for using them was emission compliance.

And as far as magnetos and reliability - there is a good reason they
use two!!! Many "experimental" planes are using electronic ignition
on at least one set, and there are STCs (Supplemental Type
Certivicates) to allow installation of electronic ignitions (like
lightspeed) on virtually ANY certified plane. With the electronic
ignition systems you get more power and better fuel burn (lower fuel
consumption) as well as generally easier starting, as well as better
plug life, less fouling, - all advantages when an old "tractor engine"
is all that's keeping your ass in the air.

Clare Snyder,
Technical Director
RAA (Recreational Aircraft Association) Canada

On Thu, 05 Jun 2014 20:56:41 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

fired this volley in
:

Combined with a digital delay. The spark timing and the pulse on the
position sensor are 2 totally different points in time, with the
actual ignition event timing being calculated by the microcomputer
based on the input from intake air temperature, throttle position
and/or Manifold Absolute Pressure and/or Mass Airflow sensor, plus

Snicker! We're talking about a kid's two-cylinder MOTOSICLE! Not a
friggin CAR!

LLoyd G
And some of todays "motorsicles" are more sophisticated in their
engine management than many cars (They have to be to put out the power
they do and still meet emission requirements)

I understand this is LIKELY some old beater of a bike with a
relatively unsophisticated "points replacement" kettering electronic
ignition - in which case the difference in coil resistance may cause
problems but is quite unlikely to be the cause of a (measureable)
timing error.

On Thu, 05 Jun 2014 21:08:02 -0400, Steve Walker
wrote:

On 6/4/2014 9:15 PM, wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same.

No, it shouldn't. Very few bikes fired both cylinders at the same time.
How many cylinders, what type of bike, what year?



The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric

On a parallel twin they will fire exactly at the same time or exactly
180 or 360 degrees apart. The timing spec before or after TDC will be
the same on both cyls UNLESS there is a cooling issue that woulds have
one cyl a few degrees off to prevent heat related detonation issues
and the like (like #3 cyl on the old beetle engine, which with the
Bosch 009 distributor, had a 2 or 3 degree retard.

On a V twin, one cyl MAY be retarded for the same reason. The OP still
has not indicated what make, model and vintage this "scoot" is - and
without that information we are all just guessing.

On 2014-06-05, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

(gotta be two, unless they were really dolts and paralleled two
coils!)

That's on the assumption that both coils fire at the same time, but of
course, if they don't then why are there two coils?

If one fires too quickly after the other, there may not be
sufficient time to build up the field for the second one.

I know that my wife's Mazda RX-2 (Wankel engone) had two
distributors, two coils, and two spark plugs per rotor -- one near the
leading edge and one near the trailing edge. At a guess, this was to
ensure more complete combustion.

It made it fun trying to figure out how many cylinders for
income tax purposes (when you got different mileage allowances depending
on the number of cylinders. So to analyze it:

Actual number of cylinders: 0

Number of rotors: 2

Number of spark plugs: 4

Number of firing strokes per rev: 6 (three per rotor -- about
equivalent to a V12).

So -- how many cylinders could I claim? :-)

Enjoy,
DoN.

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In article , DoN.
Nichols wrote:

On 2014-06-05, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

(gotta be two, unless they were really dolts and paralleled two
coils!)

That's on the assumption that both coils fire at the same time, but of
course, if they don't then why are there two coils?

If one fires too quickly after the other, there may not be
sufficient time to build up the field for the second one.

I know that my wife's Mazda RX-2 (Wankel engone) had two
distributors, two coils, and two spark plugs per rotor -- one near the
leading edge and one near the trailing edge. At a guess, this was to
ensure more complete combustion.

It made it fun trying to figure out how many cylinders for
income tax purposes (when you got different mileage allowances depending
on the number of cylinders. So to analyze it:

Actual number of cylinders: 0

Number of rotors: 2

Number of spark plugs: 4

Number of firing strokes per rev: 6 (three per rotor -- about
equivalent to a V12).

So -- how many cylinders could I claim? :-)

Depends on the *exact* wording of the law, but I bet that you can claim
zero and cite the definition. For a parallel, look up the history of
the mansard roof architecture of houses.

Joe Gwinn

On 2014-06-06, Joe Gwinn wrote:
In article , DoN.
Nichols wrote:

[ ... ]

I know that my wife's Mazda RX-2 (Wankel engone) had two
distributors, two coils, and two spark plugs per rotor -- one near the
leading edge and one near the trailing edge. At a guess, this was to
ensure more complete combustion.

It made it fun trying to figure out how many cylinders for
income tax purposes (when you got different mileage allowances depending
on the number of cylinders. So to analyze it:

Actual number of cylinders: 0

Number of rotors: 2

Number of spark plugs: 4

Number of firing strokes per rev: 6 (three per rotor -- about
equivalent to a V12).

So -- how many cylinders could I claim? :-)

Depends on the *exact* wording of the law, but I bet that you can claim
zero and cite the definition. For a parallel, look up the history of
the mansard roof architecture of houses.

I'm sure that I *could* have claimed zero without problems, but
it would have been more to my benefit (at that time) to claim 8 or 12.
There was a higher deduction for mileage with the larger number of
cylinders. :-)

Claiming 4 would have been safe enough (and I think that is what
I did), since I could say that I counted spark plugs. :-) But that would
have been no better than claiming zero -- the borderline was between
four and eight. :-)

Enjoy,
DoN.

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Email: | (KV4PH) Voice (all times): (703) 938-4564
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On Thu, 05 Jun 2014 16:54:37 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Dan sez:

The condenser across the points keeps the voltage from arcing at the
points. You might swap the condensers and see if that changes things.
If it does one of the condensers is bad.

We stopped using the term "condenser" in the 1960s G

WE auto mechanics (and parts mfgrs) were all still calling them
condensers in the late '80s, when I got out.


ANYway... that's not all the capacitor does. It also controls the decay
time of the field in the coil. And that depends upon the inductance of
the coil -- the old "LC constant".

If the coils are noticably different in resistance, there's a really good
chance they have pretty large differences in numbers of turns. That
vastly affects the inductance of the coil.

I wonder how critical that is in that application. I think I missed
the OP.


If you wish to have both coils "fire" at the same time, you must have
them inductively matched, and have the same capacitance across both sets
of points (gotta be two, unless they were really dolts and paralleled two
coils!)

Yes, ideally.


Don't forget point gap. If there are two sets, then if they're not
gapped exactly the same, the timing will change there, too.

Two new coils, two new capacitors, and two new sets of points are the
best way to go. (might as well throw in plugs and HT wires, too...)

OK, Mr. Deep Pockets Shotgunner. heh heh heh

--
It is characteristic of all deep human problems that they are
not to be approached without some humor and some bewilderment.
-- Freeman Dyson

On Fri, 06 Jun 2014 09:35:30 -0400, Joe Gwinn
wrote:

In article , DoN.
Nichols wrote:

On 2014-06-05, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

(gotta be two, unless they were really dolts and paralleled two
coils!)

That's on the assumption that both coils fire at the same time, but of
course, if they don't then why are there two coils?

If one fires too quickly after the other, there may not be
sufficient time to build up the field for the second one.

I know that my wife's Mazda RX-2 (Wankel engone) had two
distributors, two coils, and two spark plugs per rotor -- one near the
leading edge and one near the trailing edge. At a guess, this was to
ensure more complete combustion.

It made it fun trying to figure out how many cylinders for
income tax purposes (when you got different mileage allowances depending
on the number of cylinders. So to analyze it:

Actual number of cylinders: 0

Number of rotors: 2

Number of spark plugs: 4

Number of firing strokes per rev: 6 (three per rotor -- about
equivalent to a V12).

So -- how many cylinders could I claim? :-)

Depends on the *exact* wording of the law, but I bet that you can claim
zero and cite the definition. For a parallel, look up the history of
the mansard roof architecture of houses.

Joe Gwinn
Would not be to your advantage to claim 0. The correct claim would be
6. In effect it is a 6 cyl 2 stroke engine. Horsepower and fuel
economy to match.

On Fri, 06 Jun 2014 19:18:59 -0700, Larry Jaques
wrote:

On Thu, 05 Jun 2014 16:54:37 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Dan sez:

The condenser across the points keeps the voltage from arcing at the
points. You might swap the condensers and see if that changes things.
If it does one of the condensers is bad.

We stopped using the term "condenser" in the 1960s G

WE auto mechanics (and parts mfgrs) were all still calling them
condensers in the late '80s, when I got out.

Folks here in my parts of Cali still call em condensers. Go to NAPA
and ask for a condenser and they will trot em out.




ANYway... that's not all the capacitor does. It also controls the decay
time of the field in the coil. And that depends upon the inductance of
the coil -- the old "LC constant".

If the coils are noticably different in resistance, there's a really good
chance they have pretty large differences in numbers of turns. That
vastly affects the inductance of the coil.

I wonder how critical that is in that application. I think I missed
the OP.


If you wish to have both coils "fire" at the same time, you must have
them inductively matched, and have the same capacitance across both sets
of points (gotta be two, unless they were really dolts and paralleled two
coils!)

Yes, ideally.


Don't forget point gap. If there are two sets, then if they're not
gapped exactly the same, the timing will change there, too.

Two new coils, two new capacitors, and two new sets of points are the
best way to go. (might as well throw in plugs and HT wires, too...)

OK, Mr. Deep Pockets Shotgunner. heh heh heh

"Libertarianism IS fascism... Fascism is corporate government – a Libertarian’s wet dream"
Tala Brandeis
Owner at Tala Brandeis Associates"

On Thu, 05 Jun 2014 21:08:02 -0400, Steve Walker
wrote:

On 6/4/2014 9:15 PM, wrote:
My son asked me and I didn't know the answer so I thought I'd pose it
here. His bike has two ignition coils. The coils are not the same,
they are from different years of manufacture for different models of
motorcycle. The timing is not the same for each cylinder, but should
be the same.

No, it shouldn't. Very few bikes fired both cylinders at the same time.
How many cylinders, what type of bike, what year?

IRRC..my BMW R90/6 fires both at the same time..using 2 different
coils





The coils have different resistance. My son was wondering
if the difference in timing could be because one coil takes longer to
build up enough voltage to cause the spark plug to spark. The coils
are connected to the same control box. So I'm wondering if the voltage
rise from two ignition coils could be that much different.
Eric


"Libertarianism IS fascism... Fascism is corporate government – a Libertarian’s wet dream"
Tala Brandeis
Owner at Tala Brandeis Associates"

On Thursday, June 5, 2014 7:25:28 PM UTC-4, wrote:







As regards the need for matched coils

you are right, he should be using the correct matched coils. I have

told him this. He continues to half ass the work on this bike and I

continue to give him **** for it. But his question got me wondering so

that's why I posted it here.

Eric

Before I ran out and bought matched coils, I would swap coils and see how that affects the timing. The coils may have nothing to do with the timing. Indeed I doubt if that the coils affect the timing.

Dan