My neutral light went on the blink at about 50k miles. It was the plunger, and that's on the back of the engine behind the coolant bottle and swingarm. Contrary to the manual, you don't need to take the swingarm out to replace it, just take out the battery and unfasten the water coolant bottle and swing it out of the way. It's a fiddle, but easily done if you're even half mechanically competent. A couple of hours of swearing will do it! I think a new plunger is about 30 quid though