Timing Light?
Thread Starter
Senior Member
Joined: Oct 2003
Posts: 352
Judge Ito's comments on the use of a two-stroke timing light got me to thinking. I posted a reply to his timing thread but I think in the recent chaos it was lost.
My background is in two-strokes. I raced jetskis for several years and have built motors that have qualified for and raced at the IJSBA World Finals back in the day. I'm no dummy when it comes to such things but will never claim to know everything. I've never found a need for a two-stroke light. A two-stroke twin set up to fire in waste-spark will fire both plugs every 180* of crank rotation. When using a timing light this will cause the beam to bounce back and forth between the timing indicator and the opposite side of the wheel. Not a big deal really. You can still obtain a very accurate adjustment. The indicator flashes on and off versus staying solidly lit.
In my understanding the rotary works the same way for the leading plugs. It takes three revolutions of the e-shaft to produce one full revolution of a rotor. Since the combined faces of a twin-rotor motor add up to six spark events from the stock waste-spark configuration (dealing with an FC specifically) we're ending up with the same two-stroke, waste-spark results that we have with the two-stroke twin. Which is to say that the plugs are triggered every 180* of e-shaft rotation. Just like Judge Ito says.
My question is then, why would the timing be skewed (Ito briefly mentioned halving the indicated numer) other than the obvious trigger event 180* off location?
Judge? Anyone? Thanks!
My background is in two-strokes. I raced jetskis for several years and have built motors that have qualified for and raced at the IJSBA World Finals back in the day. I'm no dummy when it comes to such things but will never claim to know everything. I've never found a need for a two-stroke light. A two-stroke twin set up to fire in waste-spark will fire both plugs every 180* of crank rotation. When using a timing light this will cause the beam to bounce back and forth between the timing indicator and the opposite side of the wheel. Not a big deal really. You can still obtain a very accurate adjustment. The indicator flashes on and off versus staying solidly lit.
In my understanding the rotary works the same way for the leading plugs. It takes three revolutions of the e-shaft to produce one full revolution of a rotor. Since the combined faces of a twin-rotor motor add up to six spark events from the stock waste-spark configuration (dealing with an FC specifically) we're ending up with the same two-stroke, waste-spark results that we have with the two-stroke twin. Which is to say that the plugs are triggered every 180* of e-shaft rotation. Just like Judge Ito says.
My question is then, why would the timing be skewed (Ito briefly mentioned halving the indicated numer) other than the obvious trigger event 180* off location?
Judge? Anyone? Thanks!
Fabricator
Joined: Jan 2004
Posts: 1,322
From: Central Ohio (Hebron) Zephyrhills Fla.
C. Ludwig,Dec 14 2004, 12:13 PM
Judge Ito's comments on the use of a two-stroke timing light got me to thinking. I posted a reply to his timing thread but I think in the recent chaos it was lost.
My background is in two-strokes. I raced jetskis for several years and have built motors that have qualified for and raced at the IJSBA World Finals back in the day. I'm no dummy when it comes to such things but will never claim to know everything. I've never found a need for a two-stroke light. A two-stroke twin set up to fire in waste-spark will fire both plugs every 180* of crank rotation. When using a timing light this will cause the beam to bounce back and forth between the timing indicator and the opposite side of the wheel. Not a big deal really. You can still obtain a very accurate adjustment. The indicator flashes on and off versus staying solidly lit.
In my understanding the rotary works the same way for the leading plugs. It takes three revolutions of the e-shaft to produce one full revolution of a rotor. Since the combined faces of a twin-rotor motor add up to six spark events from the stock waste-spark configuration (dealing with an FC specifically) we're ending up with the same two-stroke, waste-spark results that we have with the two-stroke twin. Which is to say that the plugs are triggered every 180* of e-shaft rotation. Just like Judge Ito says.
My question is then, why would the timing be skewed (Ito briefly mentioned halving the indicated numer) other than the obvious trigger event 180* off location?
Judge? Anyone? Thanks!
If you have the divide by two feature on your light, it can be used to get a brighter flash from Doctor Edgertons fabulous invention. The longer dwell time gets the brighter flash.
Some years of rotaries use the wasted spark on the leading plugs, so there are two flashes per revolution, no mater if you have the front leading or the rear leading hooked up, and that makes for a less bright flash from the gun. (twice as many flashes as you need).
No such problem when checking the trailing plugs, as there is no wasted spark and only one spark per revolution per plug is used.
You may have to pull the trigger a few times to get it hitting on the pulse that is intended to light number one, but the flash will be bright enough to time it in bright sunlight.
It works great on lost spark 2 cycles as well.
There is also a feature on many guns to adjust in a number of degrees of rotation right on the back of the gun. So, when there are only two marks on the pulley and neither one is anywhere near what timing you are after, you can start at the -5 degree mark dial up 25 degrees on the gun and when you rev the engine, it will appear as though there is a mark at 20 degrees. Damn clever idea. There is a two week school involved, and more than the $10.00 I paid for the last gun I bought.
Lynn E. Hanover
Judge Ito's comments on the use of a two-stroke timing light got me to thinking. I posted a reply to his timing thread but I think in the recent chaos it was lost.
My background is in two-strokes. I raced jetskis for several years and have built motors that have qualified for and raced at the IJSBA World Finals back in the day. I'm no dummy when it comes to such things but will never claim to know everything. I've never found a need for a two-stroke light. A two-stroke twin set up to fire in waste-spark will fire both plugs every 180* of crank rotation. When using a timing light this will cause the beam to bounce back and forth between the timing indicator and the opposite side of the wheel. Not a big deal really. You can still obtain a very accurate adjustment. The indicator flashes on and off versus staying solidly lit.
In my understanding the rotary works the same way for the leading plugs. It takes three revolutions of the e-shaft to produce one full revolution of a rotor. Since the combined faces of a twin-rotor motor add up to six spark events from the stock waste-spark configuration (dealing with an FC specifically) we're ending up with the same two-stroke, waste-spark results that we have with the two-stroke twin. Which is to say that the plugs are triggered every 180* of e-shaft rotation. Just like Judge Ito says.
My question is then, why would the timing be skewed (Ito briefly mentioned halving the indicated numer) other than the obvious trigger event 180* off location?
Judge? Anyone? Thanks!
If you have the divide by two feature on your light, it can be used to get a brighter flash from Doctor Edgertons fabulous invention. The longer dwell time gets the brighter flash.
Some years of rotaries use the wasted spark on the leading plugs, so there are two flashes per revolution, no mater if you have the front leading or the rear leading hooked up, and that makes for a less bright flash from the gun. (twice as many flashes as you need).
No such problem when checking the trailing plugs, as there is no wasted spark and only one spark per revolution per plug is used.
You may have to pull the trigger a few times to get it hitting on the pulse that is intended to light number one, but the flash will be bright enough to time it in bright sunlight.
It works great on lost spark 2 cycles as well.
There is also a feature on many guns to adjust in a number of degrees of rotation right on the back of the gun. So, when there are only two marks on the pulley and neither one is anywhere near what timing you are after, you can start at the -5 degree mark dial up 25 degrees on the gun and when you rev the engine, it will appear as though there is a mark at 20 degrees. Damn clever idea. There is a two week school involved, and more than the $10.00 I paid for the last gun I bought.
Lynn E. Hanover
Senior Member
Joined: Jan 2002
Posts: 1,915
From: NJ USA
Originally Posted by Syonyk' date='Dec 20 2004, 06:16 AM
Ito - you should really have your own website with all this wealth of knowledge available. Or at least an archive of it or something.
-=Russ=-
-=Russ=-
Senior Member
Joined: Jan 2003
Posts: 983
From: redondo beach
Originally Posted by Judge Ito' date='Dec 20 2004, 04:10 PM
Senior Member
Joined: Nov 2001
Posts: 574
Originally Posted by Judge Ito' date='Dec 20 2004, 04:10 PM
Notes are good. Forum Tips are good
Senior Member
Joined: Nov 2001
Posts: 2,284
The Walmart in my area didn't have any timing lights. 
I need a cheap one with a decently fast flash circuit so it can keep up when hooked to leading (you know, because leading flashes twice as often as when hooked to one of the trailing plug wires).
I need a cheap one with a decently fast flash circuit so it can keep up when hooked to leading (you know, because leading flashes twice as often as when hooked to one of the trailing plug wires).
