OK, speculation it is.
Rider A had a micro nuclear war head installed on his bike for "defense" against a rival MC. Unfortunately, the launch trigger was located right next to the high beam switch and was accidentally thumbed when the rider attempted to hit the high beam for better vision when rider B began to outpace rider A. The problem was that the missile bay doors were not opened prior to launch so the missile could not exit the vehicle. The rocket impulse of the missile drove rider A's bike into rider B's bike and the missile subsequently detonated resulting in catastrophic failure of both bikes. The truth will unlikely ever be reported as the micro-nuclear device was designed to "self-clean" on detonation so that no evidence of the device would remain. As such, this accident will likely be chalked up to the more mundane drinking and driving/rider error scenario's that we all know are simply scapegoats for the real issue.
Or maybe it was a deer strike.