The MD6 air filter has a cleanable element permanently installed in the air
intake assembly. It is basically a mesh of steel similar to steel wool.
The air intake assembly should be washed regularly with solvent and then
re-oiled with a light weight oil to aid in trapping the dust.
The only engine drain plug is situated on the left side of the engine, near
the oil dip stick. Most engines have this drain made by screwing together
two separate fittings. One is an angled piece into which the drain valve is
attached. If you remove the drain valve first, the angled piece can be
removed from the block. It is then possible to ream the drain passage with
a long, small diameter twist drill should it be clogged with debris. The
drain passage connects in a straight line to the passages in the head.
I can forward pictures of both of the above items to anyone who may be
interested.
Best regards
Perry Basden
Windsor, Ontario