450EXC 2010 one year old. Always started first turn on the starter until a few months ago. Now it turns over the engine at what seems a reasonble speed but will not start. It starts real easy on the kickstart, one gentle kick and it fires up straight away on tickover. Hot or cold makes no difference. I 've checked the valve clearances (so has MotoExtereme at Marshfiled). The battery is showing over 13 plus bought a new one just in case. Generator output is fine. I've cleaned out the carb and fitted another iridium spark plug. The starter has been taken off and the brushes checked (again by MotoExtereme). Anyone got any other ideas please?