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YO-233-B2A Engine Maintenance Manual
TEO-540-A1A Engine Maintenance Manual
(3) Cylinder Overspeed Inspection
(a) Complete the cylinder compression pressure check on all cylinders to complete the
check of the sealing quality of the rings and valves. Refer to the section "Cylinder
Compression Check Procedure" in Chapter 72-30.
(b) Use a borescope or equivalent instrument to examine the walls of each cylinder for
scoring which could be caused by a stuck or broken piston ring. Refer to the
"Cylinder Borescope Inspection Procedure" in Chapter 72-30.
(4) Valve Train Overspeed Inspection
(a) Either repeated moments or short periods of operation in the overspeed region
increase the rate of wear at an accelerated rated in the parts that make up the valve
train and consequently decrease engine reliability. In addition to the checks completed
on the engine during a 100-hour maintenance inspection, complete the following steps
to examine the valve train before putting the engine back into service.
(b) Use a borescope or equivalent illuminated magnifying optical device to examine the
condition of the intake and exhaust valve faces and seat faces. If there is evidence of
excessive wear, pounding, or grooving, replace the valve and seat.
(c) Examine the external condition of valve keys, rockers, and exhaust valve guides for
damage. Examine valve springs for coil strikes or severe bottoming of the coils. If
damage to springs is evident, remove them and complete the check of the
compression load as specified in the latest revision of the Service Table of Limits -
SSP-1776. Replace any valve spring that is not within limits.
(d) Rotate the crankshaft by hand to see if the valve lift is uniform or equal for all
cylinders. See if valve rockers are free when the valves are closed. Unequal valve lift
is an indication of bent push rods. Tight rockers, when valves are closed, are an
indication of a tuliped valve or a damaged valve lifter. Repair any suspected damage
before putting the engine back into service.
(e) Refer to the latest revision of Service Bulletin No. 388 to determine exhaust valve
condition and stem-to-valve guide clearance condition.
C. Incorrect Fuel or Fuel Contamination
Actual damage to the engine from incorrect fuel could be in a range from unnoticeable to
(1)
severe damage or failure. Primary damage to the engine caused by incorrect fuel occurs
in the combustion chambers. Tuliped intake valves and burned pistons from excessive
cylinder head and oil temperatures are evidence of primary damage. If detonation has
been severe enough, further damage will occur to crank pins, main bearings,
counterweights, and valve train components. The extent of damage can vary accordingly
as the duration of run, engine power level and the type of fuel used.
Any mixture of unapproved fuels and additive materials that change the octane rating.
(2)
© 2021 Avco Corporation. All Rights Reserved
February 2021
AVOID FLIGHT IF A LOWER OCTANE OR INCORRECT GRADE
OF FUEL OR JET FUEL. (DIFFERENT FROM FUEL IDENTIFIED IN
APPENDIX A IN THE YO-233-B2A INSTALLATION & OPERATION
MANUAL) IS USED TO OPERATE THE ENGINE. UNUSUAL
DETONATION CAN INCREASE ENGINE TEMPERATURE AND
PRESSURE WHICH CAN DAMAGE THE ENGINE.
05-50
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