2008 Suzuki LT-A400/F, LT-F400/F ATV Service Manual, Page 173Get this manual
Fuel System:
Main System As the throttle valve (1) is opened, engine speed rises and negative pressure in the venturi "A" increasesThis causes the piston valve (2) to move upwardThe fuel in the float chamber (3) is metered by the main jet (4)The metered fuel enters the needle jet (5), mixes with the air admitted through the main air jet (6) and forms an emulsionThe emulsified fuel then passes through the clearance between the needle jet (5) and jet needle (7) and is discharged into the venturi "A", where it meets the main air stream being drawn by the engineMixture proportioning is accomplished in the needle jet (5)The clearance through which the emulsified fuel must flow ultimately depends on throttle position