The America , Speedmaster , Bonneville and Thruxton all have that tube. As they all have the same engine cases.
It allows oil to drain down from the head and helps equalize any air pressure differnce between the head and the crankcase.
I have over 11k on my bike and never had a leak I did not cause.
These bikes are very reliable and do not have the demons( lucas or oil leaks) the older bikes had.
It may not be oil.
The bikes shipped from triumph have way to much cosmoleen(sp?) on some of the parts.
I had a hell of a time getting it all off my Daytona.
