1986-1989 Honda TRX250 FourTrax 250R Service Manual, Page 52Get this manual
FUEL SYSTEM
CARBURETOR THEORY
FLOAT CHAMBER
The float valve and float maintain constant fuel level in the float chamber The loat level affects the mixture throughout the entire range- Although it is possible to alter the fuel mixture by changing the loat leve l, it is not recommended
(1) FLOAT VALVE (2) FLOAT
STARTINGIDLE CIRCUIT
When the choke valve is opened (knob up), fuel is metered by the starter jet and is mixed with air from the primary air passage to provide rich mixture to ease startingWhen the choke va lve is closed (knob down), it reduces the mixture to more normal level for idlingWith the knob down, the actual flow of fuelair is regulated by the adjustment of the chokeidle speed knob The end of the threaded chokeidle speed knob acts as miniature throttle valve in the primary air jet passageWith the knob threaded all the way down, it cuts off all fue lair from this passage (no idle speed) and with it threaded all the way up, it allows maximum amount of fuelair through this passage (high idle speed) This circuit has two main functions; to start cold engine (knob up) or to supply enough fuelair to allow the engine to idle (knob down and adjusted properly)(4) ORIFICE