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'80-'82 XS400 SOHC Twins with Mikuni BS34 Carbs

This is the second gen XS400 carbs which are BS34 Mikuni carbs. This was the second version of the BS34 that mounted the jets to the body instead of to the float bowl itself. These carbs used the normal larger diaphragm found on other Yamaha BS34's from this era.  They are also easy to mix-up due to the ID number being acid etched into the upper bell housing and hard, if not impossible, to read. All of the carbs listed here are basicly the same other than the '82 XS400S having some black coated brackets. 

Note: Starting in '74 Yamaha started year coding bikes in the last letter used in the name. You may see this code on your bikes paperwork or in a parts list or catalog.  I leave this off as it is redundant if you are showing the year anyway. There is a chart below to find your year code.

Below is a set of '80-'81 XS400 3F9 Mikuni BS34 carbs. They were converted to use the later style fiber float that works much better than the brass floats they used from the factory. Making this change you have to also alter to the correct float height measurement for this type float. '82-'83 XS650 float height measurement works for this (22.4mm).

'80-'81 XS400-----------------------------------------3F9
'80-'81 XS400S Special---------------------------3F9
'82 XS400S Special--------------------------------14V