ET: Engine (Twin) Oil Leak

Cyborg

Well Known and Active Forum User
VOC Member
Further to fitting the D breather on the front spring cap. The first photo shows a C front head and it has both the crescent shaped reliefs top and bottom. The second photo shows a head that came out of the factory quite late. It doesn’t have the relief on the bottom so more restrictive if used with a D breather cap. Not much air gets past the top relief because it is almost sealed off by the rocker bearing. Without the relief on the bottom, it severely limits the ability of air getting through the two drain grooves, so more air would be forced through between the rocker bearing and rocker arm. It would be interesting to see a photo of a known original D front head. Was the bottom relief left out intentionally or was someone asleep at the switch.....
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oexing

Well Known and Active Forum User
VOC Member
In an engine in good condition there is not sooo much air coming out of the breather - basically. So some groove on the rocker bearing should do to pass air .

Vic
 

vibrac

Well Known and Active Forum User
VOC Member
With a small tubular PCV valve there is no flow of air once pressures have equalized the french letter test proved that years ago
Remember on the Egli racer we had one valve on front exhaust cap and one on rear inlet up through the pipe via the PCV valve and down to a single catch tank (ACU size 500cc) total oil for season I desert spoon full.
90 % of breather oil output is because of engine condition
 
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