Timing light question!
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Joined: Nov 2021
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From: Georgia
Timing light question!
When it comes to timing on a sportster, I understand the static timing as manual gives you step by step directions. I'm curious about the dynamic timing which uses a timing light. The only experience I have had with a timing light was pretty much watching my pops back in the day when he was timing car motors and what not. So, I'm kind of hoping for a little schooling on my part to just learn how the light works. I know you hook it up to a battery source and put the clamp around from spark plug wire. Then with RPM's up around 1500 or so, watch for the line to be centered in the timing hole. What's got me scratching my head is the dial on the timing light to adjust the advance on the light itself. I have a 2002 sportster with a 505/515 cam in the motor. My question is what should that dial be set on to properly see the line in the center based on that cam. Adjusting that dial while motor is running you can move that line either way using the timing light dial. So, what should that dial be set to? I'm sure you wouldn't leave it at zero.
Just trying to learn a little from some that know a little about timing that way and how the timing light should be used properly. I would be appreciative.
Thanks
Just trying to learn a little from some that know a little about timing that way and how the timing light should be used properly. I would be appreciative.
Thanks
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From: Honah Lee
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A 2002 with it's stock ignition is what's called a "dual-fire" ignition, meaning that whenever it generates a spark for a given cylinder, the other cylinder also gets a spark, even though that other cylinder is not positioned for combustion. This additional spark is referred to as the "wasted spark".
You can, if you choose, upgrade the ignition and coil to a "single-fire" system, which fires the two cylinders independently, i.e. no wasted spark occurs.
This is germane to your question, because dual fire really complicates using a timing light on a motor, and what's more, dual fire confuses the hell out of a "dial-back" timing light, which it sounds like you have.
To use a timing light, you remove that little plug on the right side of the motor, that sits right between the two cylinders. Hook up the timing light's inductive pickup to the front spark plug wire and start the motor and point the timing light there.
First thing you'll notice is oil all over the place. You can buy a clear timing plug to stop the oil splashing in your face, but it's already difficult to see the flywheel marks with the timing light, and the clear plug makes it even more difficult.
Next thing you'll notice is extraneous flashes. That's because the timing light is flashing both for the front cylinder's spark (the one you want) and the rear cylinder's spark (the one you don't want), because when the rear cylinder hits, the front gets a wasted spark. So now you're looking in this little hole, with oil everywhere, getting flashes from the timing light, half of which are meaningless. It's just a difficult process.
Because of the engine's single crank-pin 45 degree design, the spark interval on a Harley is 405 degrees, followed by 315 degrees, followed by 405 degrees, 315 degrees, etc etc ad infinitum. So they're not coming at nice consistent intervals, not when you've got a dual-fire system.
This is a problem for dial back timing lights. The way a dial back light works is that it sees the spark at the spark plug, it waits a little bit of time (the amount of which is determined by the dial position), and then it flashes. The idea is to put the flash at the front cylinder's TDC mark on the flywheel, which is a vertical line, instead of the dots on the flywheel that indicate the proper amount of advance at idle speed. So you just point the light at the flywheel and turn the dial until the front TDC line is centered in the window and read the timing advance off the dial.
So how long does it wait? Well, the dial back light calculates how long to wait, between the spark and the flash, based on the rpm of the engine. It knows by measuring the interval between the spark, which tells it the rpm, which establishes how long it is from the spark to the TDC mark.
The timing light is made for a single fire system, because that's what virtually all cars use. It's assuming that sparks are coming every 720 crankshaft degrees, which is the firing interval for single-fire. So it's calculating the engine's rpm, and the corresponding amount of time delay from spark-to-flash, based on an assumption that the spark is coming every 720 degrees.
But a dual fire system is sparking at this odd 315-405-315-405 interval. None of the intervals are anywhere near 720 degrees, they average out to every 360 degrees which is twice as often. Therefore the spark-to-flash delay is based on bad data and the delay is all wrong.
Here's the bottom line. Using a timing light on a Harley is a difficult process to begin with, between the visibility issue and the extraneous flashes. A dial-back light with a dual fire system doesn't work, it gives the wrong result because the firing interval isn't 720 degrees.
You are, in my opinion, a ton better off to set your timing statically. Do it carefully and it's going to be more accurate than doing it with a light.
I used to be associated with a company that sold roughly 1,000 engine kits a year, most of those for Sportsters. Those kits live or die based on the accuracy of the tuning. Done wrong and the kit gets destroyed. This is especially true of the ignition timing. So in our kit installation instructions, we emphasized how important it is to set the timing correctly. We specifically stated to set it using the static method. The above is the reason why. We also created a video to show how to statically time the ignition, and set it's DIP switches, for use with our kits. The timing light method is just too tedious and error-prone. Others may disagree, but when you're in the engine kit business, you can't ask your customers to perform a difficult, error-prone process. The process has to be straightforward and easy and accurate. Static timing is all of those things.
You can, if you choose, upgrade the ignition and coil to a "single-fire" system, which fires the two cylinders independently, i.e. no wasted spark occurs.
This is germane to your question, because dual fire really complicates using a timing light on a motor, and what's more, dual fire confuses the hell out of a "dial-back" timing light, which it sounds like you have.
To use a timing light, you remove that little plug on the right side of the motor, that sits right between the two cylinders. Hook up the timing light's inductive pickup to the front spark plug wire and start the motor and point the timing light there.
First thing you'll notice is oil all over the place. You can buy a clear timing plug to stop the oil splashing in your face, but it's already difficult to see the flywheel marks with the timing light, and the clear plug makes it even more difficult.
Next thing you'll notice is extraneous flashes. That's because the timing light is flashing both for the front cylinder's spark (the one you want) and the rear cylinder's spark (the one you don't want), because when the rear cylinder hits, the front gets a wasted spark. So now you're looking in this little hole, with oil everywhere, getting flashes from the timing light, half of which are meaningless. It's just a difficult process.
Because of the engine's single crank-pin 45 degree design, the spark interval on a Harley is 405 degrees, followed by 315 degrees, followed by 405 degrees, 315 degrees, etc etc ad infinitum. So they're not coming at nice consistent intervals, not when you've got a dual-fire system.
This is a problem for dial back timing lights. The way a dial back light works is that it sees the spark at the spark plug, it waits a little bit of time (the amount of which is determined by the dial position), and then it flashes. The idea is to put the flash at the front cylinder's TDC mark on the flywheel, which is a vertical line, instead of the dots on the flywheel that indicate the proper amount of advance at idle speed. So you just point the light at the flywheel and turn the dial until the front TDC line is centered in the window and read the timing advance off the dial.
So how long does it wait? Well, the dial back light calculates how long to wait, between the spark and the flash, based on the rpm of the engine. It knows by measuring the interval between the spark, which tells it the rpm, which establishes how long it is from the spark to the TDC mark.
The timing light is made for a single fire system, because that's what virtually all cars use. It's assuming that sparks are coming every 720 crankshaft degrees, which is the firing interval for single-fire. So it's calculating the engine's rpm, and the corresponding amount of time delay from spark-to-flash, based on an assumption that the spark is coming every 720 degrees.
But a dual fire system is sparking at this odd 315-405-315-405 interval. None of the intervals are anywhere near 720 degrees, they average out to every 360 degrees which is twice as often. Therefore the spark-to-flash delay is based on bad data and the delay is all wrong.
Here's the bottom line. Using a timing light on a Harley is a difficult process to begin with, between the visibility issue and the extraneous flashes. A dial-back light with a dual fire system doesn't work, it gives the wrong result because the firing interval isn't 720 degrees.
You are, in my opinion, a ton better off to set your timing statically. Do it carefully and it's going to be more accurate than doing it with a light.
I used to be associated with a company that sold roughly 1,000 engine kits a year, most of those for Sportsters. Those kits live or die based on the accuracy of the tuning. Done wrong and the kit gets destroyed. This is especially true of the ignition timing. So in our kit installation instructions, we emphasized how important it is to set the timing correctly. We specifically stated to set it using the static method. The above is the reason why. We also created a video to show how to statically time the ignition, and set it's DIP switches, for use with our kits. The timing light method is just too tedious and error-prone. Others may disagree, but when you're in the engine kit business, you can't ask your customers to perform a difficult, error-prone process. The process has to be straightforward and easy and accurate. Static timing is all of those things.
Last edited by aswracing; Yesterday at 08:47 AM.
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From: Santa Ana, CA
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From: The Wasteland
A 2002 with it's stock ignition is what's called a "dual-fire" ignition, meaning that whenever it generates a spark for a given cylinder, the other cylinder also gets a spark, even though that other cylinder is not positioned for combustion. This additional spark is referred to as the "wasted spark".
You can, if you choose, upgrade the ignition and coil to a "single-fire" system, which fires the two cylinders independently, i.e. no wasted spark occurs.
This is germane to your question, because dual fire really complicates using a timing light on a motor, and what's more, dual fire confuses the hell out of a "dial-back" timing light, which it sounds like you have.
To use a timing light, you remove that little plug on the right side of the motor, that sits right between the two cylinders. Hook up the timing light's inductive pickup to the front spark plug wire and start the motor and point the timing light there.
First thing you'll notice is oil all over the place. You can buy a clear timing plug to stop the oil splashing in your face, but it's already difficult to see the flywheel marks with the timing light, and the clear plug makes it even more difficult.
Next thing you'll notice is extraneous flashes. That's because the timing light is flashing both for the front cylinder's spark (the one you want) and the rear cylinder's spark (the one you don't want), because when the rear cylinder hits, the front gets a wasted spark. So now you're looking in this little hole, with oil everywhere, getting flashes from the timing light, half of which are meaningless. It's just a difficult process.
Because of the engine's single crank-pin 45 degree design, the spark interval on a Harley is 405 degrees, followed by 315 degrees, followed by 405 degrees, 315 degrees, etc etc ad infinitum. So they're not coming at nice consistent intervals, not when you've got a dual-fire system.
This is a problem for dial back timing lights. The way a dial back light works is that it sees the spark at the spark plug, it waits a little bit of time (the amount of which is determined by the dial position), and then it flashes. The idea is to put the flash at the front cylinder's TDC mark on the flywheel, which is a vertical line, instead of the dots on the flywheel that indicate the proper amount of advance at idle speed. So you just point the light at the flywheel and turn the dial until the front TDC line is centered in the window and read the timing advance off the dial.
So how long does it wait? Well, the dial back light calculates how long to wait, between the spark and the flash, based on the rpm of the engine. It knows by measuring the interval between the spark, which tells it the rpm, which establishes how long it is from the spark to the TDC mark.
The timing light is made for a single fire system, because that's what virtually all cars use. It's assuming that sparks are coming every 720 crankshaft degrees, which is the firing interval for single-fire. So it's calculating the engine's rpm, and the corresponding amount of time delay from spark-to-flash, based on an assumption that the spark is coming every 720 degrees.
But a dual fire system is sparking at this odd 315-405-315-405 interval. None of the intervals are anywhere near 720 degrees, they average out to every 360 degrees which is twice as often. Therefore the spark-to-flash delay is based on bad data and the delay is all wrong.
Here's the bottom line. Using a timing light on a Harley is a difficult process to begin with, between the visibility issue and the extraneous flashes. A dial-back light with a dual fire system doesn't work, it gives the wrong result because the firing interval isn't 720 degrees.
You are, in my opinion, a ton better off to set your timing statically. Do it carefully and it's going to be more accurate than doing it with a light.
I used to be associated with a company that sold roughly 1,000 engine kits a year, most of those for Sportsters. Those kits live or die based on the accuracy of the tuning. Done wrong and the kit gets destroyed. This is especially true of the ignition timing. So in our kit installation instructions, we emphasized how important it is to set the timing correctly. We specifically stated to set it using the static method. The above is the reason why. We also created a video to show how to statically time the ignition, and set it's DIP switches, for use with our kits. The timing light method is just too tedious and error-prone. Others may disagree, but when you're in the engine kit business, you can't ask your customers to perform a difficult, error-prone process. The process has to be straightforward and easy and accurate. Static timing is all of those things.
You can, if you choose, upgrade the ignition and coil to a "single-fire" system, which fires the two cylinders independently, i.e. no wasted spark occurs.
This is germane to your question, because dual fire really complicates using a timing light on a motor, and what's more, dual fire confuses the hell out of a "dial-back" timing light, which it sounds like you have.
To use a timing light, you remove that little plug on the right side of the motor, that sits right between the two cylinders. Hook up the timing light's inductive pickup to the front spark plug wire and start the motor and point the timing light there.
First thing you'll notice is oil all over the place. You can buy a clear timing plug to stop the oil splashing in your face, but it's already difficult to see the flywheel marks with the timing light, and the clear plug makes it even more difficult.
Next thing you'll notice is extraneous flashes. That's because the timing light is flashing both for the front cylinder's spark (the one you want) and the rear cylinder's spark (the one you don't want), because when the rear cylinder hits, the front gets a wasted spark. So now you're looking in this little hole, with oil everywhere, getting flashes from the timing light, half of which are meaningless. It's just a difficult process.
Because of the engine's single crank-pin 45 degree design, the spark interval on a Harley is 405 degrees, followed by 315 degrees, followed by 405 degrees, 315 degrees, etc etc ad infinitum. So they're not coming at nice consistent intervals, not when you've got a dual-fire system.
This is a problem for dial back timing lights. The way a dial back light works is that it sees the spark at the spark plug, it waits a little bit of time (the amount of which is determined by the dial position), and then it flashes. The idea is to put the flash at the front cylinder's TDC mark on the flywheel, which is a vertical line, instead of the dots on the flywheel that indicate the proper amount of advance at idle speed. So you just point the light at the flywheel and turn the dial until the front TDC line is centered in the window and read the timing advance off the dial.
So how long does it wait? Well, the dial back light calculates how long to wait, between the spark and the flash, based on the rpm of the engine. It knows by measuring the interval between the spark, which tells it the rpm, which establishes how long it is from the spark to the TDC mark.
The timing light is made for a single fire system, because that's what virtually all cars use. It's assuming that sparks are coming every 720 crankshaft degrees, which is the firing interval for single-fire. So it's calculating the engine's rpm, and the corresponding amount of time delay from spark-to-flash, based on an assumption that the spark is coming every 720 degrees.
But a dual fire system is sparking at this odd 315-405-315-405 interval. None of the intervals are anywhere near 720 degrees, they average out to every 360 degrees which is twice as often. Therefore the spark-to-flash delay is based on bad data and the delay is all wrong.
Here's the bottom line. Using a timing light on a Harley is a difficult process to begin with, between the visibility issue and the extraneous flashes. A dial-back light with a dual fire system doesn't work, it gives the wrong result because the firing interval isn't 720 degrees.
You are, in my opinion, a ton better off to set your timing statically. Do it carefully and it's going to be more accurate than doing it with a light.
I used to be associated with a company that sold roughly 1,000 engine kits a year, most of those for Sportsters. Those kits live or die based on the accuracy of the tuning. Done wrong and the kit gets destroyed. This is especially true of the ignition timing. So in our kit installation instructions, we emphasized how important it is to set the timing correctly. We specifically stated to set it using the static method. The above is the reason why. We also created a video to show how to statically time the ignition, and set it's DIP switches, for use with our kits. The timing light method is just too tedious and error-prone. Others may disagree, but when you're in the engine kit business, you can't ask your customers to perform a difficult, error-prone process. The process has to be straightforward and easy and accurate. Static timing is all of those things.
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From: Honah Lee
@Bubba Zanetti Thank you. Just added this to my Sticky Timing a Sportster.
So what you are saying or impying is use the static method? You sure that plug on a Sportster is on the right side?
So what you are saying or impying is use the static method? You sure that plug on a Sportster is on the right side?
Last edited by Jackie Paper; Yesterday at 10:02 AM.
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From: Honah Lee
Thank you. Some of those YouTube are sneaking other Harleys in there. And that screw in plug we are referring too is not the timer cover.
Last edited by Jackie Paper; Yesterday at 10:36 AM.
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From: Santa Ana, CA
@Bubba Zanetti Thank you. Just added this to my Sticky Timing a Sportster.
So what you are saying or impying is use the static method? You sure that plug on a Sportster is on the right side?
So what you are saying or impying is use the static method? You sure that plug on a Sportster is on the right side?