Carburetor Circuits; Carburetor Adjustments; Carburetor Servicing; Slow And Mid-Range - Kohler KS530 Service Manual

Fuel System

Carburetor Circuits

Float
Fuel level in bowl is maintained by fl oat and fuel inlet
needle. Buoyant force of fl oat stops fuel fl ow when
engine is at rest. When fuel is being consumed, fl oat will
drop and fuel pressure will push inlet needle away from
seat, allowing more fuel to enter bowl. When demand
ceases, buoyant force of fl oat will again overcome fuel
pressure, rising to predetermined setting and stop fl ow.

Slow and Mid-Range

At low speeds engine operates only on slow circuit. As
a metered amount of air is drawn through slow air bleed
jets, fuel is drawn through main jet and further metered
through slow jet. Air and fuel are mixed in body of slow
jet and exit to idle progression (transfer port) chamber.
From idle progression chamber, air fuel mixture is
metered through idle port passage. At low idle air/fuel
mixture is preset and not adjustable. This mixture is then
mixed with main body of air and delivered to engine.
As throttle plate opening increases, greater amounts of
air/fuel mixture are drawn in through fi xed and metered
idle progression holes. As throttle plate opens further,
vacuum signal becomes great enough at venturi so main
circuit begins to work.
Main (high-speed)
At high speeds/loads engine operates on main circuit.
As a metered amount of air is drawn through air jet,
fuel is drawn through main jet. Air and fuel are mixed
in main nozzle then enters main body of airfl ow where
further mixing of fuel and air occurs. This mixture is then
delivered to combustion chamber. Carburetor has a fi xed
main circuit; no adjustment is possible.

Carburetor Adjustments

NOTE: Carburetor adjustments should be made only
after engine has warmed up.
Carburetor is designed to deliver correct fuel-to-air
mixture to engine under all operating conditions. Main
fuel jet is calibrated at factory and is not adjustable. Idle
fuel is also set at factory and is not adjustable.
Low Idle Speed (RPM) Adjustment
NOTE: Actual low idle speed depends on application.
Refer to equipment manufacturer's
recommendations.
1. Low idle speed (without governor) for basic engines
is 1200 RPM (± 75 RPM). This can be adjusted by
holding throttle lever against stop and turning low
idle speed screw in or out.
2. These engines have governed idle. To set to
manufacturer's recommendation, turn adjustment
screw on speed control bracket in (clockwise) to
increase or out (counterclockwise)to decrease RPM
speed.
High Speed (RPM) Adjustment
1. With engine running, move throttle control to fast
and pin.
2. Loosen speed control bracket mounting screws,
slide bracket to adjust high speed setting, then
tighten screws.
30

Carburetor Servicing

NOTE: Main and slow jets are fi xed and size specifi c.
Fixed jets for high altitudes are available.
● Inspect carburetor body for cracks, holes, and other
wear or damage.
● Inspect fl oat for cracks, holes, and missing or
damaged fl oat tabs. Check fl oat hinge and shaft for
wear or damage.
● Inspect fuel inlet needle and seat for wear or damage.
● Inspect spring loaded choke plate to make sure it
moves freely on shaft.
1. Perform removal procedures for appropriate air
cleaner and carburetor outlined in Disassembly.
2. Clean exterior surfaces of dirt or foreign material
before disassembling carburetor. Remove bowl
retaining screws and carefully separate fuel bowl
from carburetor body. Do not damage fuel bowl
O-rings. Transfer any remaining fuel into an
approved container. Save all parts.
3. Remove fl oat pin, fl oat, and inlet needle. Seat for
inlet needle is serviceable by replacing carb spacer
(inlet seat assembly). Remove carb spacer by
carefully lifting up and off carburetor body.
NOTE: Lift straight up and not sideways to ensure main
tube isn't damaged.
4. Main jet can be removed from carb spacer by using
a blunt tool and gently pushing jet out of center
stem. Main jet is retained in carb spacer by O-ring.
Inspect O-ring during disassembly and replace if
damaged. Repair kits are available for both gravity
and fuel pump equipped engines.
5. Clean carburetor bowl and assembly as required.
6. See illustration for carburetor components on page
28. Note O-ring on carb spacer to carburetor body
and fuel bowl, inlet seat/spacer well and main jet.
Cleaning of passages and orifi ces can be done
using compressed air. Do not use wire or carburetor
cleaner.
7. After cleaning, inspect choke shaft and choke valve
assembly for wear. Replace as required with choke
shaft kit. To install kit go to step 8, otherwise go to
step 10. Inspect throttle shaft and throttle valve
assembly. If wear is found on throttle shaft, install
throttle shaft kit. To install kit go to step 10, otherwise
go to step 12. If wear is noted within choke and/or
throttle shaft bores of carburetor body, a complete
carburetor replacement is recommended.
KohlerEngines.com 22 690 01 Rev. --