Autonerdz forums

First off a huge thanks for Spence for getting these captures. I agree with you guys on the leaning towers, I think its mostly due to both the compression release and crank speed variation as it is a 45 degree twin with common crankpin so front cylinder fires, 315 degrees later rear cylinder fires, 405 degrees later front cylinder fires.
Interestingly, this is one of the reasons Harley dominated flat track for such a long time as this pop..pop firing maximized traction by giving the tire "time" to recover. The Japanese played with  this in road racing with their "Bg Bang" motor as well.
On my problem motor I am not able to capture a CKP trace as its an older carburated motor. I run into this a lot as many motorcycles are still carburated. I have build a remote starter with a 60 tooth gear and VRS mounted on it to use on some of these staggered firing motors. I use it on the end of the crank to turn the motor over. Unfortunately can’t on this motor.
I have a fair bit less intake vacuum than yours, could this partly be due to the fact that you have a common intake manifold where mine is individual runners with a carb and filter on each end? Also, my running compression seems much too high.  I am going to redo the compression waveforms now that I have adjusted the valve clearance and I’ll post them to compare.

James, keep in mind if the timing is off by a significant amount this could also raise the compression as allowing the intake more time too inhale, just a thought there, much like cranking comp is higher than running..........has more time to inhale.

Run into this in GDI motors ( a little different example, but similar) if the pump is initiatated too early (out of time advanced) the pressures can go up in the thousands as the build time is far longer.............. very interesting.

The nice thing as we talked about here is learning the different subtle nuances of how each system works and then you have a base line for repairing said system.  The beauty of the Pico is you have knowledge of as you stated the differnt firing times of both cyclinders on the Harley, now you can watch it in real time...............and is it right or is it wrong????, that will be developed over time.