19-04-15, 08:56 AM
Carb gaskets: I've always been able to re-use the big ones that seal the float bowls.
I have had an O-ring that seals the brass needle valve body fail, which caused a carb to flood. This doesn't sound like your problem, but if you're pulling them out for cleaning and inspection they may not survive re-insertion… it's best to replace. There are complete pattern kits of everything rubber (and the needle valve) for the float bowls available at about £18 per carb (don't bother to look at genuine Yamaha prices), but as the little O-rings are probably all you'll need you can get a universal assortment box for about £5.
Taking them on and off is a bit of a faff so if you've an extra length of petrol hose and a separate petrol reservoir, it's worth checking that the fuel levels are correct while the carbs are on the workbench.