Sounds like the fuel pump is struggling for fuel to me Theres filters inside the tank as well as the inline one next to the pump https://www.2fiftycc.com/index.php?threads/fzr250-3ln-fuel-system.1804/
Awesome dude thank you so much. Will let you know how I get on as well - Will be a while as I've got to wait for my litetek bits/keyster kits to arrive and then get my mechanic to do all the hard work ( every time i type that out i feel less of a man ) but after carbs are rebuilt will definitely give you some feedback after I've put some miles through them . Went and got a socket set and pulled off the seat so I could have a look at the exup servomotor - the noise definitely isn't coming from there. Tried feeling around for vibrations but it's somewhere under RHS fairing and I don't have a square drive and whatever else i'd need to take it off. Yes I could buy one.. But it's beer time now and I really would rather pay the bike wizard to deal with it It could well be the butterfly itself but I couldn't feel anything thru the exhaust. And on the servo side, the cable appears to pull itself normally. I ordered the Venhill exup replacement kit anyway just in case. Even if the cable turns out fine it should be handy to have. Again thanks heaps for your time!
edit: This would actually make sense if there was crud in the fuel tank, right? I was doing 110ks for a good while with less than 1/2 tank of fuel. Good info , I plan to get my wizard to check the whole fuel system and while he's in there check on the exup too. I would like to get this girl running again before she's offline for carb rebuild and valve clearances etc.. Only put about 150 or so kms on her, had an absolute blast and now she's just sitting there like some kind of sad orange paperweight Thanks!
I'm useless and won't be doing it myself, but I will make sure my mechanic has a look at this when all the kits arrive from you/keyster. Thanks mate