Whilst flying in a field recently, the prop did a lot of grass
cutting and bits must have got into the engine (Irvine 46) and
got burnt. As a result I have a blackened piston and liner - I
assume this is a layer of carbon - that I can't seem to remove.
1. Will this do the engine any harm? - I haven't really noticed
any loss of performance, but the engine seems to run a little
2. What is the best way to get rid of it and return to gleaming
I don't really think that grass getting into the engine will have
caused much damage. Blackened piston & liners are usually
caused by the accumulated carbon from the burning of fuel.
will build up over a few years. Initially, it probably helps seal
the piston and liner giving good compression.
when the build up becomes excessive, power will decrease noticeably.
Only then contemplate removal of the liner.
can then remove the deposits with very fine wet and dry paper
lubricated with machine oil. Move up and down the liner in a figure
of eight action. But gently does it.
on the piston can be removed n the same way. Clean all parts thoroughly.
You dont want any swarf to enter the engine!
the engine, but don't be afraid when the compression is awful.
You will have to run a few tanks of fuel though it before the
piston & liner bed in again.
to conclude I don't think your engine has come to any harm. It
seems that what you are seeing are the natural effects of normal
engine running. You shouldn't unnecessarily take your engine apart
and most defiantly not try to return the piston & liner to
the gleaming example you had when you bought the engine.
contemplate the above procedure when there has been a very noticeable
loss of power that cannot be attributed to anything else. This
usually happens on quite old engines.
recently revitalised an old HGK45 in this way. But then this engine
was 18 years old!