Mk2 breather valve

I just bought the big brass breather valve for my MK2 850 from Norvil after advice from Les. This apparerntly goes half way along the 1/2inch bore pipe from the outlet on the RH timing cover to the oil tank neck (reducing though to 3/8inch near the oil tank). I also bought the two parts manuals for the Mk2 but the breather valve is not in their? Is it actually for a MK2 and not a Mk3? Which way round does it fit? Does it blow out of the timing cover to the oil tank or the other way round as it is a one way valve?

They were not factory installed, therefore have no factory part numbers. The direction of flow is from the cranckcases to the oil tank.

If you look at the breather valve body, there should be an arrow on it showing the direction that the air goes, which is away from the engine. You can check by blowing into each end, one end will allow air to pass through, blowing at the other end will not.

These are not standard, as Maylar says. I fitted mine behind the airbox when I had one fitted to my bike. I have reservations about this plumbing based valve that Norvil sells. In my opinion, it is better to have this type than nothing, but on the one that I had from Norvil needed a bit of pressure to lift the valve from its seat and let air pass through unlike the reed valve type.

The reed valve type that I now have on (the XS type) is much lighter and more compact, and lets air pass through it at a low er initial pressue.

Thanks. Yes it does take a little pressure to lift it off but I guess if there is no pressure then there is no issue to fix. Guess a reed would be better though.