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Crankcase Ventilation System; Governor - Onan MicroLite 2800 Series Service Manual

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Disconnect the ignition shut down circuit by locat-
ing relay K3 (Figure 7-3) and removing leads G2-1
and S2-1 from K3-30. Separate piggy backed leads
G2-1 and S2-1 and insulate them from each other
and from ground.
Remove the spark plug, reconnect the spark plug
lead and ground the plug side electrode to bare
metal on the engine.
not touch the plug or plug wire during testing.
Crank the engine and observe the plug. A good
spark should be observed. If no spark is observed,
the magneto or wires connected to the magneto are
the most likely cause. Refer to the Generatorsection
for generator disassembly to access the magneto
The crankcase breather prevents pressure from build-
ing up in the crankcase.
also prevents oil contamina-
tion by removing moisture or gasoline vapors and other
harmful blow-by materials from the crankcase. These
vapors are routed to the carburetor where they are
mixed with the incoming air and burned in the combus-
tion chamber. A sticky breather valve can cause oil
leaks, high oil consumption, rough idle, reduced engine
power, and a rapid formation of sludge and varnish
within the engine.
Crankcase Breather Service
If the crankcase becomes pressurized, as
evidenced by oil leaks at the seals, use the following
procedures to service.
Remove the breather tube and the head cover (see
Engine Block Assembly, Section 9) then remove the
breather from the cylinder head and inspect it. The reed
valve must be flat with no sign of creases or other
damage. If the breather is defective, replace it. If the
breather is dirty, clean it in parts cleaning solvent.
Most parts cleaning solvents are
flammable and can result in severe
personal injury if used improperly. Follow the manu-
facturer's recommendations when cleaning parts.
Check breather tube and air passages for clogging and
clean as required.
The governor controls engine speed which directly
affects the voltage output and frequency of the genera-
tor. An increase in engine speed will cause a corres-
ponding increase in generator voltage and frequency. A
decrease in engine speed will cause a corresponding
decrease in generator voltage and frequency. The gov-
ernor maintains a constant engine speed under chang-
ing load conditions so that generator voltage and fre-
quency do not vary.
Governor Adjustments
Contact with moving parts can cause
severe personalinjury Keep clothing,
jewelry, bands, and fingers dear while adjusfing the
A hof generator set can cause severe
burns. Always allow fhe generator
set to cool before touching any components
ing any parts.
Before making governor adjustments, run the unit about
15 minutes under 50percent load to reach normal oper-
ating temperature. If governor is completely out of
adjustment, makea preliminary adjustment at no load to
first attain a safe voltage and speed operating range.
An accurate voltmeter and frequency meter should be
connected to the generator in order to correctly adjust
the governor (accuracy of 0.3% on frequency and 0.5%
on voltage). A small speed drop not noticeable without
instruments will cause an objectionable voltage drop.
A binding in the governor shaft, governor linkage, or
carburetor throttle will cause erratic governor action or
alternate increase and decrease in the engine speed
(hunting). A rich or lean carburetor adjustment can
cause hunting and a fouled spark plug can cause miss-
ing and hunting. Springs tend to lose their calibrated
tension through fatigue and after long usage and may
require replacement.
If the governor action is erratic after adjustments are
made, replace the spring. If this does not improve opera-
tion, the problem may be within the governor mecha-
nism (see Engine Block Assembly, section 9).
Adjustments to the governor should be made in the
following sequence.
The carburetor fuel mixture screws must be cor-
rectly adjusted before governor adjustments are
made. If the carburetor needs adjusting, refer to the
Mixture Screw Adjustments in this section before
making any adjustments to the governor.
Set the carburetor throttle stop screw as specified in
Carburetor Mixture Screw Adjustments (step 5).
Check the governor linkage for binding or exces-
sive looseness. Check the motion spring for bend-
ing or damage and straighten or replace as needed.
With unit operating at no-load, adjust the speed
adjustment screw (see Figure 6-6) on the governor
obtain 62.5
0.5 Hz, at between 120 and
126 volts on 60 hertz units. Set 50 hertz units to
obtain 52.0
at between 220 and 231 volts
for 220 volt units and 240 to 252 volts for 240 volt
6-1 0
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by any means, is strictly prohibited.


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  • Jim May 26, 2019 07:14:
    I have an Onan MicroLite 2800 2.8 KY. I was told I should start it every two weeks and let it run for 15 minutes or so. I don't find anything in the manual about doing that. Please explain what I need to do.
  • Brian Nov 26, 2018 02:36:
    I like your website, which has been helpful in researchin​g the problem with my Onan MicroLite 2800 generator. Having a complete service manual online is great. However, the wiring diagram clearity is so poor I cannot read most of them. For example, on page 57, figure 8-1 has so many designatio​ns missing that the figure is almost worthless. Is there any way the schematic can be reproduced so as to be of use? Thanks a lot.