Timing advance curves

Can anybody tell me why there are two different curves in a timing advance graph in the manual? I can’t seem to find any answers to this in the forums. My apologies in advance if it’s already been explained somewhere. Any information is greatly appreciated.

That chart doesn't really show two different curves.
It shows timing advance in relation to engine speed.
The right hand line is full advance approaching 2000 rpm and above.

Agreed, the area between the lines should be "shaded" for clarity. E.G.: the graph for my "K" shows an upper reading of 41.5 and a lower reading of 38.5 at full advance (factory spec is 40) this is in part due to manufacturing tolerances of all the components involved (bob weights, spring tension etc) All "mass produced" components have a "tolerance"
This is in part why modern engines of smaller capacity make more power, where ignition curves and fuelling can be "mapped" to get the best out of the motor.

Those curves are from a 1984 GPz 1100. It does not have a mechanical advancer. The advance is electronic within the igniter.

There will still be manufacturing differences between the components involved (trigger, pick up coils etc) the area between the two lines represents "in spec"

Thanks but I’d bet that has nothing to do with it. 

Wozza and loudhvx answered this question in 2018 on this site.

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This is why I typically don’t have anything to do with forums. You can ask a question and you never get an answer from somebody who actually knows what they’re talking about. It’s just a guess. Like this. And then there is the snark. Some keyboard warrior in the clique who’s got to prove you’re wrong. With a crayon. It’s a guess. You don’t know what you’re talking about. Nothing proves what you’re saying. Somebody else said it on the site. So what. Where is the proof? Again, it’s an electronic ignition. No mechanical parts. No wear and tear. It doesn’t happen when it’s electronic. If you don’t really know the answer, keep it to yourself.

Just another example of a topic/issue/question that has been covered in the past here. The amount of info on site is a great resource when one can find it or it is pointed out by another member who has found it.

Just another post by a snarky guy whose opinion nobody really cares about and needs to get off the keyboard to go get drunk or something. I already said that I looked for it and couldn’t find it. And if I had, it would have been irrelevant to the question anyway. Have you ever noticed when you look at a curve on an electronic ignition today, there’s just one? Not two. Because it’s electronic. I don’t care if you can’t understand that. Go away.

Sounds like you’re projecting. No need to be a child. 

the tolerance in timing error doesn’t come from the electronic ignition. It comes from the accuracy of drilling the dowel pin that determines TDC in the end of the crank. The crank end  diameter is so small that even a couple thousandths difference can equate to a few degrees of timing error. I personally have found 1-2 degrees timing error on different cranks from the era. Nothing to do with the ignition system at all. 

I’m projecting? I’m a child? Look in the mirror. Why did you feel it was necessary to make this stupid arrogant pointless post? Another member of the old clique who felt it was extremely important to defend the status quo. Again, you prove my point. Just trying to make yourself appear intelligent and knowledgeable? Guess what? You failed. You’re not. Who is really the child here? It’s you. Grow up before it’s too late. Get over it. It’s ok. Really. And by the way, who asked you anyway? You really felt it was necessary to make this waste of everyone’s time post? Why? Get over yourself. Go do something useful. Watch TV. Go to bed.