Generator Drive Belt Tension - Lycoming O-290 Operator's Manual

LYCOMING OPERATOR'S MANUAL
O-235 AND O-290 SERIES
AFTER ALL CYLINDER BASE NUTS HAVE BEEN TIGHTENED, REMOVE ANY NICKS IN
THE CYLINDER FINS BY FILING OR BURRING.
(9) Assemble each push rod in its respective shroud tube, and assemble each rocker in its respective
position by placing rocker between bosses and sliding valve rocker shaft in place to retain rocker.
(10) O-290-D2 Series – Be sure that the piston is at top center compression stroke and that both valves
are closed. Check clearance between the valve stem tip and the valve rocker. In order to check this
clearance, place the thumb of one hand on the valve rocker directly over the end of the push rod
and push down so as to compress the hydraulic tappet spring. While holding the spring
compressed, check valve clearance, which should be between .028 and .080 inch. If the clearance
does not come within these limits, remove the push rod and insert a longer or shorter push rod, as
required to correct clearance.
(11) O-235, O-290-D Series – Be sure that the piston is at top center compression stroke and that both
valves are closed. Assemble adjusting screw in valve rockers and using clearance gage adjust the
clearance between the valve tip and valve rocker. Adjust in the following manner:
Set tappets with .007 in. - .009 in. clearance cold. Recheck tappet clearance after run-in,
clearance should be from .006 in. to .012 in. After adjusting, lock the adjusting screw in place with
the locknut.
(12) All Engines – Install gaskets and rocker box covers, intake pipes, drain tubes and exhaust
manifold. Install spark plugs and ignition harness.
5. GENERATOR DRIVE BELT TENSION. Check the tension of a new belt 25 hours after installation. Refer
to latest revision of Service Instruction No. 1129 for methods of checking generator drive belt tension.
Inserting a long rod will cause a decrease in valve clearance.
CAUTION
NOTE
MAINTENANCE PROCEDURES
SECTION 5
5-9