4. Fuel System
4-2
Maintenance Information
Precautions in Operations
Warning
Gasoline is a highly flammable material and may explosive under circumstance. Thus, always work in a
well-ventilated place and strictly prohibit flame when working with gasoline.
y Care must be taken when dealing with gasoline, and always work in a well-ventilated place and strictly
prohibit flame.
y When disassembling fuel system parts, pay attention to O-ring position, replace with new one as
re-assembly
y It has to conduct air bleeding operation as removed the oil tube.
y Idle speed adjustment.
Specification
Item Jet 4 R 50
Ventura diameter 15 mm
Idle speed
1900±100 rpm
Throttle handle free play 2~6 mm
Troubleshooting
Engine cannot be started
1. No fuel in fuel tank
2. Fuel can not reach to carburetor
3. Too much fuel in cylinder
4. Clogged air cleaner
Stall after started
5. Incorrect idle speed adjustment
6. No spark on the spark plug
7. Low compression pressure
8. Rich mixture
9. Lean mixture
10. Clogged air cleaner
11. Inlet pipe leaking
12. Polluted fuel
Lean Mixture
1. Clogged carburetor jet
2. Clogged hose from carburetor to canister
3. Bend, squeezed or clogged fuel lines
4. Clogged fuel filter
5. Malfunction of float valve
6. Low fuel level in float chamber
7. Clogged vent pipe
8. Malfunction of fuel pump
Rich Mixture
13. Malfunction of float valve
14. Low fuel level in float chamber
15. Clogged carburetor air injector
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