yep same once u give it some hard revs it just chirps away from what feels like behind the bars ? couldn't find it for ages then the other day bang lol its so simple what i haven't don't is tapped the flap down yet to find out if its the flap or the actual cap. it stops when i hold the cap but that could just be cushioning the vibration to the flap lol i tried some sticky back foam the other day which made it worse so im thinking along the lines of a small bit of heavy duty velcro

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Yamaha xt660x 2009 blue/gold mods= iridium plug, stage1+2, removed snorkel, blocked ais, akrapovric pipes, power commander pc3usb (pre made map), adjusted tps, dynojet 02 optimiser 30amp aux relay, smoked puig screen, oxford heated grips and brembo carbon ceramic pads, rfx 30mm bar raisers, puig long adjustable leavers, plus much more and a cheep �30 alarm which stopped it been stolen