Carburetor; Construction; Function And Operation Of Throttle Valve - RedMax GZ25N Workshop Manual

7. CARBURETOR

7-1 Construction

The Strato-charged Engine is applied with a custom designed carburetor employing diaphragm rotary
valves and 2 venturies, one for the lead air and the other for the air-fuel mixture.
Air Cleaner

7-2 Function and Operation of Throttle Valve

unit: mm
Venturi bore
8
8
9
9
The throttle valve has 2 ports. Upper port is for
the lead air and lower port for the air-fuel mixture.
As shown above, the rotary valves are coaxially
arranged while their air passage bores and valve
outside diameters differ each other. As the venturi
bore sizes also differ each other, air intake timing
can be changed by rotation of the rotary valves.
Lead Air
A
B
Carburetor
18.1
Lead Air block
Air-fuel Mixture
block
13.0
Rotary Valve
18
18
STRATO CHARGED ENGINE GZ25N
STRATO CHARGED ENGINE GZ25N
Lead Air Intake Tube
Insulator
Air-fuel Mixture
Throttle Valve
A : Lead Air Port
: Air-fuel mixture Port
B
Intake timing for the air-fuel mixture and the
lead air are as illustrated below:
Idling
Lead air : Close
Mixture : Start to open
Mid speed
Lead air : Start to open
Mixture : Half open
High speed
Lead air : Full open
Mixture : Full open
To Reed Valve