Testing Carburetor - Bosch PB-650 Service Manual

PB-650
PB-750

4-4 Testing carburetor

2K209A
FUEL SYSTEM
1. To fill and wet fuel pump circuit with fuel, push
purge pump several times.
2. Pull off black fuel line from carburetor and con-
nect pressure tester 897803-30131 (A) to fuel inlet
on carburetor.
3. Apply pressure to aprrox. 0.8 kgf/cm
The pressure should remain over 0.5 kgf/cm
4. If it drops below 0.5 kgf/cm
pump cover and repeat the previous Step 3. If it
still drops rapidly, proceed to Step 6 to locate the
leak.
5. Apply pressure to 0.5 kgf/cm
purge pump. Pressure should drop. If it does not
drop, check the metering lever height for too low of
a setting (according to "4-7 Checking metering
lever"), or Inlet needle valve for sticking (according
to "4-8 Checking inlet needle valve").
6. Remove fuel return pipe and throttle wire from
carburetor, then remove carburetor from engine.
With pressure tester still attached, submerge car-
buretor in suitable clean solvent and apply 0.5 kgf/
cm 2 (7 psi) pressure to locate the leak.
7. If the air bubbles come out between the pump
body and the carburetor body, check the pump dia-
phragm, pump gasket, and diaphragm seat of
carburetor body.
8. If the air bubbles come out from the carburetor
bore, check inlet valve, metering lever spring and
the metering lever height.
21
2 (10 psi).
2
(7 psi).
2
(7 psi), re-tighten
2 (7 psi) and push