Oil tank breather

Hi
Had my Commando for 10ys 850 mk2a 1975, had the engine rebuilt in 2006 with few problems, always ran the engine on Duckhams 20/50 Classic mineral, however i am no longer able to get this oil and have changed to Castrol Classic X/L20/50, the only diff is the oil looks a lot thicker than the Duckhams and i have started getting problems with oil spitting out the oil tank breather, the breather pipe that is on the neck of the filler just below the filler cap its a short pipe that just runs down the tank and points towards the battery tray, the other breather goes into the casing that houses the timing chain, my bike has always been this way and never been a problem till i changed oil, the oil is filled to the minimum level on the dipstick and no more.
Can anyone give me advice on this one.

Thanks Neil

Neil said:

the breather pipe that is on the neck of the filler just below the filler cap its a short pipe that just runs down the tank and points towards the battery tray, the other breather goes into the casing that houses the timing chain

Click to expand...

You have them connected up the wrong way, then.

I suggest you connect the engine breather pipe as shown, and run the correct "oil tank breather" tube into a small catch bottle?