Some pointers to
standard Minor breathing arrangements.
* The earlier
cars had a pipe pointing straight down on the tappet chest cover which was the
inlet for engine breathing.
* The outlet was via the pipe on the rocker cover to the air.
* The Oil Filler Cap on these engines should be solid ( i.e. NO wire filter in it.)
* The 'straight down' pipe was found to leak oil, so was later changed to a swan's neck shape
which stopped a lot of the leakage.
* Later engines
had a different system where the breather pipe on the tappet chest went
straight to either a valve device on the inlet manifold and then to the carb. Or, straight to the carb so this was now the outlet and necessitated a change
in the Oil Filler Cap which now had a wire filter in it and had become the
So the rules are:-
* If your engine
breathes into the air filter it should have a 'solid' oil filler cap.
* If it breathes into the carb the filler cap should have the wire filter in it
and the rocker cover should not have a breather pipe on it.
* These filter
type caps are supposed to be changed every 12,000 miles but can be
thoroughly cleaned with a good de-greaser etc.
* If the revs
rise considerably when the filler cap is removed then the wire filter is clogged
Hope this helps...
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