Reply To: Miss and backfire under 5k only after engine warms up – 2009 GT650R
If the cylinder is cold = No sparks are happening , so check again that it is sparking,
Swap the coils & caps front and back , then the rear cylinder should be cold , and front hot
If it makes no difference swapping ignition parts = Then check the harness is actually sending signals on those lines otherwise you have a damaged circuit along the harness that’s leading to that coil
You also want to make sure for example front cylinder has a wire that is “BLACK with GREEN LINE” —> measure that line at the ECU end for breaks (dead signal / loss along the harness) or the meter will tell you the line is complete and there is no breaks.
You want to be sure the injectors are working ===> Start the bike as you would, if the cylinder is cold. Turn her off , then remove the spark plug of that cylinder, it should be very wet with fuel ? , if else swap injectors around. And see if the rear cylinder gets cold and front engine gets hot ?