Been there,done that:P
The problem is Simon,if it mists up to bad the bike will stop!I had three on mine in six months.The later ones have different seals fitted and a resistor type thingy to make the fuel guage react slower as it swills around the tank(especially when passing 998`s
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The first sign is normally the green indicator warning light in the dash staying on.Go see John or ring him and tell him what`s happened,it`s only a ten minute job to change,three bolts and a key reprogramme,he can do it with his eyes shut he`s done so many