The problem I have is at very low revs, from tick over to about 2k revs, which is a pain in traffic and when pulling off when you don't need high revs. I have stripped the carbs twice and they are spotless inside, I have used a air compressor to blow them through and I have totally stripped them down, as to the fuel no as I have used several different fuel stations in between, as to carb balance I would say no as I have a good idle and the bike is vibe free as an inline 4 can be. I have had bikes with out of sync carbs so I do know when the carbs are out. Another maybe related is the bike does not like choke, it now plays up and will only fire on 2 or 3, I have to knock the choke off and keep trying to start the bike, I never use to have issues with the choke,