hi i have a gilera dna 50 gp experience 2004 with a leo vince tt exhaust new rollers fitted and clutch springs allthow something sounds loose near hear had reed valves put in and rejetted but it starts and runs nicely for around 15 mins riding about and then starts gurgleing like something is bubbleing up and when i rev up more its continious i have been putting clean cold water in the water tank and when run about abit i take the cap off and its like a watery brown colour i have replaced spark plug to a nbk if you can help me much thanks ps hope to hear my fault soon