Im getting a loud noise from my bike. no idea where its coming from but sounds like the engine. it starts and go's fine but after about 20 minutes the noise starts. it sound like a loose bolt but its louder than the engine.

Sorry if this sounds a bit simple but - it's not your fan coming on is it? They can make quite a noise.

I get (what we believe to be) a bit of piston slap in my '06 Raga, when the motor gets good and hot....usually indicates it's time for me and the bike to take a little rest/cool down break. Sounds like a little bolt is rattling around inside the motor.

Richening the fuel mixture just a tad helps a bit in mine, I run closer to 75:1 when the weather gets hotter around here, with no ill-effect.

On my bike, the sound goes away when I pull in the clutch, does yours?