Identify my carb

I have a 1999 yz400f, the carb is a keihin, labeled 5BE1 01NA18. Is this factory, and what are the specs? Has a boyesen quick shot. What does this do for the bike/carb? Also has what looks like an aftermarket intake.

That's the OEM carb.  Specs can be found here:


The Quick Shot is kind of a waste of money, IMO.  No harm in it, though.  The aftermarket intake horn is probably a "Power Now" or similar device intended to stabilize intake air flow at part throttle.  It is somewhat effective on a 250F, but doesn't do much for a 400.

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