Stihl 4-MIX - Engine - Leak Down Test; Crankcase - Vacuum & Pressure Test

Check valve
adjustments
Leakage % is
indicated on gauge
that is connected
to cylinder.
Adjust regulator
gauge to the set-
point.
Engine - Leak Down Test
Test the 4-MIX® engine for leaks.
Connect the gauge to the engine and read the amount of leakage.
;
There may be a little leakage past the end-gaps of the rings. If leakage is
less than 10% the sealing of the combustion chamber is acceptable.
If leakage is over 10% you will need to identify the area of leakage and repair the
leak.
;
Listen at the muffler, carburetor, flange inlet, or where the push rods come up from
the cam. A rushing air sound should be evident at one of these locations, verifying
the location of the leakage from the engine.
The leak down tester recommended by STIHL has a smaller air inlet orifice and is designed
for testing any small engine.
Crankcase - Vacuum & Pressure Test