BS34s use an oring to seal the float valve to the carb body (see above), it is nearly always shrunk and hard and lets gas leak AROUND the float valve. Always replace them when you open up a set of BS34s for the first time.
The petcocks like everything else is 30 years old they need new rubber parts and should be buffed. I have seen the MikesXS petcocks leaking after a short time. No problems do whatever you are comfortable with. If your gas tank isn't perfect inside running without screens above the petcock is asking for trouble. Perhaps use a wrap or 2 of stainless wire around the base of mikes screens so they stay on the tubes?
Slightly related the Yamaha petcocks are a decent design, the Old Kawi petcocks (KZ1300 to be precise) were junk. They depended on a nylon cone to seal against pot metal, it didn't for very long. More than one KZ1300 engine bent the LH (sidestand, low side) rod when gasoline filled that cylinder.
The petcocks like everything else is 30 years old they need new rubber parts and should be buffed. I have seen the MikesXS petcocks leaking after a short time. No problems do whatever you are comfortable with. If your gas tank isn't perfect inside running without screens above the petcock is asking for trouble. Perhaps use a wrap or 2 of stainless wire around the base of mikes screens so they stay on the tubes?
Slightly related the Yamaha petcocks are a decent design, the Old Kawi petcocks (KZ1300 to be precise) were junk. They depended on a nylon cone to seal against pot metal, it didn't for very long. More than one KZ1300 engine bent the LH (sidestand, low side) rod when gasoline filled that cylinder.