Bang Under Fierce Acceleration

Given that it happens at 8500 rpm irrespective of throttle opening confirms to me that it is a spark issue. But what is causing it? I can't remember if you changed the crank sensor in your attempts to get a running bike this spring but that would be a likely contender as that's what triggers the sparks. A friend fitted a new crank sensor to his MS4 then found the bike ran ok but misfired at 6,500. Changing to yet another sensor cured it. Connect a diagnostic software and see if any error codes are recorded. Look for P033* or P038*

 

That's the thing, or if you can get access to an oscilloscope and check the spark patterns through the rev range. It does sound like when we used to do "kill switch drive-bys" as youths... after watching Fast Bikes videos...

 

swapping back to original crank sensor is another easy one to try, had similar experience to Derek's friend on a 996 and swapping back to original confirmed the new sensor was at fault. Symptoms were unlike yours - occasional erratic idle and varied pickup from low speed.

 

Won't do any harm. Probably won't show anything either.

 

if it loses its crank signal it would lose its injection pulse too?
if the + coils suply was lost it would possibly lose its injecter + too?

 

That did occur to me which is why I firstly suggested changing the plugs.

 

That if the sparks drop out so will the injectors, so no fuel either, but the bang from the exhaust suggests unburnt fuel in the exhaust after a misfire.

 

yip, what derik said.
the ECU drives the coils and injectors based on crank signals. injector duration is also determined by map and tps position.
its probably the same relay that powers the positive side of the coils and injectors with an ignition feed, with the triger being the - from the ECU

 

can faults are a pain. many are just spurious non errors.

 

What finm says. As far as I can tell it's probably related to the ECU not getting an immobiliser signal which in your case, it doesn't need anyway.