4RT Wasted spark ignition or not?

[jrsunt]

It appears to be that the 4rt was the first bike with batteryless fuel injection and the test bed for everything else. With regards to your tests and findings, why is the high tick over so critical for the starting procedure? 

[honda_freak]

Hi Chris

These are really good oscilloscope captures you have recorded here and will certainly benefit people when they have an ignition-related problem.

I myself am also a little surprised at how it goes from wasted spark to non-wasted spark in such a short time horizon - I would not have believed this if it were not for your fine evidence here.

I also find your note regarding an injection timing in the combustion stroke just after TDC a bit strange.

But I can also confirm that this matches my captures of injection timing in the compression stroke TDC and which occurs 25 degrees after TDC.

 

This is very important evidence of when and how the ignition system works on a Honda Montesa 4RT and other motorcycles / scooters with similar battery-less systems.

It seems that there are quite a few secrets that need to be discovered.

Just keep up the good work.

Regards
Honda Freak

[jrsunt]

Does this have any relevance to anyone’s data:

Intake valve opens   6 degrees before TDC

Intake valve closes 27 degrees after BDC

Exhaust valve opens 30 degrees before BDC

Exhaust valve closes 1 degree after TDC

 

[aussiechris]

5 minutes ago, jrsunt said:

Does this have any relevance to anyone’s data:

Intake valve opens   6 degrees before TDC

Intake valve closes 27 degrees after BDC

Exhaust valve opens 30 degrees before BDC

Exhaust valve closes 1 degree after TDC

 

It doesn't have much bearing on what we've been discussing but it does show that these engines have a very short overlap (just 7° in your case).  But thanks for posting it.

I'm guessing the cam profiles changed slightly over the years/models.  These are the figures from my 2022 301RR...

14° of overlap in this case.

[jrsunt]

Wish I understood the data, I have no idea what the red or blue lines indicate 🤣( X axis crank degrees and time?  Y axis voltage?)
That was from my 250 manual. Looks like Honda freak was also been testing the 250. 

[aussiechris]

Honda_freak can answer you better but I believe the red line on both his captures is cylinder pressure.

In the most recent pic, the blue line is the fuel injector voltage.  In his earlier image, the blue line was the ignition coil secondary voltage.

He is showing the relationship between those voltages and the crank position based on cylinder compression pressure.

It's not easy to directly correlate time on the x-axis with degrees of crank rotation because during kick starting, the RPM is varying.  But it gives a good idea of what stroke it's on and roughly where in the stroke these events occur.

[honda_freak]

Hi jrsunt

Here is an explanation of this picoscope recording, which is just a simple compression test - where I measure pressure/vacuum over a period of 720 degrees, and at the same time I also measure the ignition voltage on the spark plug.

The compression test is done with the kick starter on - so the engine is not running.

The fact that the engine is not running causes the RPM to fluctuate a lot during the valve timing measurement, and therefore the measurement is not as accurate as if it were a multi-cylinder engine - where the RPM is much more stable - this is actually the same as aussiechris has explained in previous answers.

But as aussiechris writes - it can be used as a guideline regarding valve timing.