Stopping The Motorcycle; Break-In - GAS GAS EC250-4T 2010 User Manual

The slow speed necessary during the break-in period may cause
carbon to build up on the spark plug and soil it. If inspection
of the spark plug shows this to be the case, replace the standard
spark plug with a higher heat grade spark plug for the duration
of the break-in period.
Following the break-in, fit a new standard spark plug.