ignition advance really stops advancing at 3300 rpm??

There is something to be said for a good, simple tool. Especially since the 2nd gen VFRs (at least) make this easy by marking the timing on the crank gear, and having an inspection port for it. Both base and full timing are marked.

Although a timing light won't give you the precision that a scope will. But it will definitely give you an idea of what's going on. And it seems like these bikes have very, very simple-minded timing.

 

Following this thread with interest!

 

IC - I'm not sure any of us are actually going to go measure anything, just speculate on how and what we'd find...

 

LOL, this is half the fun but I'll add a photo of a few V4 guys wearing lab coats pondering over an oscilloscope would be pure gold.

 

You know, I really should pick up a lab coat at some point...

 

Actually if someone makes additional markings, between existing markings, and use a simple strobo timing light can make accurate enough measurements. A marking in the middle of the arc between the "idle advance" of let's say the 17 degrees and the "full advance" of 37 degrees will give the "27 degrees" point and in case someone makes 19 equidistant markings between the 17 and the 37 and have the appropriate timing light stability and eye sharpness can have a very accurate reading of 1 degree resolution.

If you have an oscilloscope available then you must have an audio signal generator too. All you need is to feed in the CDI an "audio" signal of 20Hz to 200Hz preferably with low duty cycle and amplitude around 0.5Volts simulating the coil input and monitor the output of the CDI with the oscilloscope. No sig-gen? well a simple 555 timer can do the job too...

I promise I will measure everything if someone assembles my bike back in a working condition.

Well I could probably get a CDI box and make these measurements on a bench as described above but my goal is to make it appealing, challenging and inventive so that someone else will do it.

Plan B is I go on with theories, everybody is getting sick and tired, and someone else finally breaks and do the measurements just to make me shut up and end the topic.

That would do too.

 

Humph....

No signal gen, aside from the laptop (but I have software for that). I mostly do high-speed stuff (hence the level of scope we have, which is way overkill for audio work). I'd been considering the 555 route, but I'm lazy. Honestly, the 20Hz to 200Hz should definitely do it, square wave, low duty cycle. What I didn't know was the voltage (and I'd rather not fry my unit). 0.5V is pretty low. Any idea what kind of input it is? (since it's clearly not a normal logic input).

 

20Hz corresponds to 1200rpm for the vf500 engine, I assume VFR700F uses the same ignition architecture, so actually what is needed for an advance graph is signal from 20 to 60Hz nevertheless 20Hz might be a challenge for many laptops.

Inductive pick up signal looks like a "one period of a sine wave" with variable amplitude as rpms increase but next the signal is fed in the box and there must be choppers/limiters. I can't recall if it was a specific VF CDI, but I have seen silicon diode CDI input choppers so in this case the peak voltage should be limited in the ±0.7 volts region.