Complex sentence: Pourcel started international motocross racing in 2004 and soon made a name for himself on the circuit, qualifying for every MX2 race even though he was riding a 125cc machine racing against 250cc machines.
Split into simpler sentences: Pourcel started international motocross racing in 2004, and soon made a name for himself on the circuit. He qualified for every MX2 race even though he rode a 125cc machine, and raced against 250cc machines.