After a dusty landing and when reassembling the engine the engine
parts should be cleaned. For all MBPROFI's I guarantee all parts for one year
(except worn pistons with more than 50 flights) as long as it is clear that
the engine ran in clean condition.
Cleaning means firstly disassembly and degreasing of all the parts. I use Acetone
for this or a similar thinner used for cellulose paint. Other products are possible
as long as all the oil and grease (especially castor oil) is radically taken
off without giving rust on the steel parts.
Clean all the parts separately. Dirt has the habit rather to
spread than to move away.
If you try for instance to clean a complete ball race in an ultrasonic cleaner,
all the dirt that is in places where it doesn't harm, will move to places where
it does.
Result: the bearing will be useless until you take it apart and clean every
part separately. The same is the case for the piston/connecting rod/piston pin
assembly.
The crankcase and the head also need their own pre-cleaning bath, they are always
very dirty on the outside, and this dirt should not reach inside areas.
Cleaning should take place in at least 2, preferably 3 stages and the last stage in a new, super clean fluid. In between the parts may be lightly brushed with a soft brush or with compressed air. Especially the ports in the cylinder need this type of attention; it is difficult to see the dirt inside the ports! Mind also the hole in the piston-pin; the dirt that comes out here will directly harm the piston skirt!
Using an ultrasonic cleaner is preferred, but the risk of spreading
the smallest particles to places where you don't want them by this process should
be envisaged.
However, a few hours in a not moving bath, is in my experience just as effective
for the last cleaning stage, as long as the right fluid is used.
Assembly of the parts should be done with clean hands in a clean
room (Which is usually not your workshop).
Take the parts you assemble directly from the clean bath, and oil them lightly
with a non-oxidating mineral oil. (Steel parts rust when they are degreased
)
Stabilised castor oil (eg Castrol A747) should be used for the big- and small
ends, for the piston pin in the piston, for the piston in the cylinder and in
all the threaded holes in aluminium. The cleaning and oiling process is very
important to prevent wear and seizure of the threads in aluminium.