G9 breather

esox · Post by **esox** » Fri Sep 17, 2010 1:50 pm

The workshop manual / maintenance guide that I have for the 1951 G9 shows a cutaway illustration of the oil tank indicating that one of the internal pipeways is related to the crankcase breather.

It is my understanding that the crankcase breather is the inch or so long metal tube emanating from the back of the crankcase & located just inboard of the rear primary chaincase.

Should I be connecting a flexible tube from this breather (if this is what it is) to one of the metal pipes coming off the back of the oil tank?

If so, which one, as there are two on the lower right hand side of the oil tank as you look at the back of it from the primary chaincase / battery carrier side?

I acquired the bike with no such flexible pipe in place - is dispensing with it a 'user' modification?

paul knapp · Post by **paul knapp** » Sat Sep 18, 2010 4:31 am

Looking at the oil tank from the battery side, as you mention, the rear most pipe on the right is the one to which the breather pipe is fitted coming from the timed breather valve on the end of inlet cam. The other one just forward, on the left, is a breather pipe going to the atmosphere, the top end is seen just inside the tank filler opening.
I think it's best to keep the breathers as original to alleviate the inclusion of any dust.

esox · Post by **esox** » Sun Sep 19, 2010 9:08 pm

Many thanks PK.
I've identified where the pipe should go & I should 'get connected' shortly.

wilko · Post by **wilko** » Mon Sep 20, 2010 2:40 am

I wonder if the breather to the tank was meant to slightly pressurise the tank to force some dribbling out to the chain as an oiler. That's how i would run the exit pipe with a bit of tubing pointing at the chain.