When balancing carbs or trying to find the location of air leaks I use a lenth of flexible tube. The diameter is not critical but something that is easily held close to the ear, long and flexible enough to be able to follow round the flanges etc that perform the supposedly air tight seal... You might hopefully be surprised just how effective it can be..?
Good luck.
I'll see if I can do something like that, but feel like it's internal for some reason.
With the engine relatively warm I started it up after repositioning the jubilee clips holding rhe hose to the TB and airfilter housing, and the whistle, which sounds more like a constant squeak, with stays when holding a steady throttle. There was a smell of petrol from the engine bay on start up but went after a few seconds of idling, but not sure if that's normal. There was, when I turned the engine off after a minutes idle, what I would describe as a relief valve going off as if letting pressure out. It used to be like a whooshing sound but has now turned to a raspy sound like you get when letting air out of a balloon.
