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Spark Timing?

  • Thread starter Thread starter genejohnson
  • Start date Start date
G

genejohnson

Guest
Maybe someone could clear up my confusion. I'm used to the wasted spark type of ignition where the plugs fire on the compression stroke and the exhaust stroke at the same time. Thus.. wasted spark. Is that the case with say the GS850. What confuses me is the two spark generators. If it is generating two different sparks, then there is two separate firings at different times? Does anyone understand my confusion? Gene
 
It's wasted spark. One coil files 1-4 & the other fires 2-3. There are two triggers 180 degrees apart that trigger one coil or the other.

Dan
 
Yup, that's the way it is. You may have noticed two separate coils on the bike. They each fire two spark plugs. The coil on the left will fire 1&4, the coil on the right will fire 2&3. Each of those pairs are the ones that share the 'wasted spark' of which you speak. However, when 1&4 are on the bottom of their respective strokes, 2&3 are at the top of their strokes, just begging for their sparks. That's why there are two sets of triggers.

Still confused? :-k

.
 
If all four coils aren't firing at the same then it is not what a "wasted spark" ignition that I am familar with does. I guess what is confusing me is the 180 degree firing. Does any cylinders fire on their exhaust stroke? Gene
 
all of them fire in the exhaust stroke at one time or another.
think of it this way... on the two cylinders #1 and #4, #1 fires on the compression stroke while #4 fires in the exhaust stroke. when #4 is firing on the compression stroke, #1 is firing on the exhaust stroke.
the same thing happens to the #2 and #3 cylinders.

genejohnson said:
If all four coils aren't firing at the same
Click to expand...
there are only two coils. each coil has two plug wires and each plug wire is connected to one end of the "coils" secondary. [spark plug]-[plug wire]-[coil secondary]-[plug wire]-[spark plug]

Bam!!! two plugs firing at one time... or is it zap?
 
Last edited:
Always wondered, if you swap the #2 & #3 or the #1 & #4 plug wire location, shouldn't the bike run exactly as if wires were in the proper locations???
 
rphillips said:
Always wondered, if you swap the #2 & #3 or the #1 & #4 plug wire location, shouldn't the bike run exactly as if wires were in the proper locations???
Click to expand...
Yes. In fact, that is a common troubleshooting tool to see if it is a wire or a plug that is causing a problem.

.
 
The timing is off the end of the crank, so it fires each revolution, not every other revolution like timing driven off the cam, which turnshalf as fast as the crank. Pistons 1 and 4 go up and down together, one on compression when the other is on exhaust. They fire at the same time. Pistons 2 and 3 go up and down together, one on compression when the other is on exhaust. They fire at the same time. So you should be able to see that each cylinder gets a spark on its exhaust stroke.
 
Thanks everyone for the patience to grill the function into my aged ole skull. I pretty much understand it now. Gene
 
Grab all four wires in your hand and crank the engine.
You will understand what a wasted spark is.
 
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