Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65 valve cover weld on thingy??

Saw this engine on eBay and noticed the weird welded on thingy on the valve cover
Ideas??

https://photos.app.goo.gl/h5CEvjfgWUFCXGwM8

Some kind of weird breather?

That was the first of the development fleegle mechanisms that
the beezer group was experimenting with in the 60's.
I'm sure one of the hardened originality enthusiasts will be able
to date the device and offer the full explanation of it's functionality.
As far as i know the project was abandoned due to the fact that
no one in the upper management even knew what the cover/casting
was off anyway.

Ha! 😂 Sounds BSA

It's a vent. Ones like this were used on valve covers of racing cars and boats.

It's a vent. Ones like this were used on valve covers of racing cars and boats.

Somebody added on to this one.

I wonder how much oil vapor coated the Right side of the head/fins?? On the + side, it likely helped with any case pressure build up related oil leaks in other places…. Maybe a race motor? Always fun to see “one mans answer”.

A 3/8 or 10mm hose fitting in the top of the timing cover is a much better breather than
those stuck into the rocker covers.

Cut a window and a couple of screw threads in the timing cover and you could mount one of these KTM 690 reed valves:

with its cover:

If you do that without reed valve, you will have troubles. More leaks.

Never found that.

Also B50’s for example (and I think triumph twins too) didn’t have a reed valve, just a large hose off the primary.

Yes but that hose went up and around the edge of the rear fender, keeping the oil in by gravity.

Devimead fitted theirs on the left side of the rocker cover on the A65, using the oil gallery to the rockers as a baffle plate.

I have also B50 for Classic Road Racing and I put there also reed valve to the breathing hose. Works very well, there is coming almost nothing to the collecting bottle.

Each to his own eh? My ones all ran primary open to crankcase, so much bigger expansion area.
Offset engines need less breathing anyway.

The triples ran the breather into the back of the air filter box. Sounds crazy, but if your air filter gets oily you need a rebuild.
My A65 came to me with an extra breather in the primary. It worked a lot better when I removed the DS crank seal. For some reason PO had put the breather in the front of the case. I ran the pipe to a Mikes XS reed valve mounted to the front of the air box (OIF.) It worked, but I had to clean the valve occasionally.