Hi! I have a Triumph Thunderbird 900 2000 mod. So without further notice I suddenly started to get a "harder" sound. These engines have this well-known "whining/whistle", but now I think it's a kind of "thud-sound" I'm hearing through the whistling, or not thud-sound either, more a "harder" sound from the motor. This happened while idling also suddenly became higher. Must fix up the carburetors but wait for parts. But can I be in my head? Or is this signs of something wrong? Maybe I haven't noticed it before?