Pipe from inlet manifold

[roys51a10]

Hi On the inlet manifold there's a pipe off not sure where it went. Haven't found any pics of it on anything else.Any ideas what it is for?

[Rocket Racer]

My guess is they have routed the timed engine breather into it so the breather is running into a vacuum. Its not uncommon to route breathers into the carbs, but its typically done into the airbox not directly into one inlet port as this appears to be. On twin carb bikes with separate ports a balance tube is quite common but that wont be the case on a shared manifold with one carb

[muskrat]

G'da Roy.
Very interesting. Where does the end of the tube go?
Is that a tap under the oil tank?
Cheers

[Swarfcut]

   I have never seen anything similar..... It's a homebrew mod.  Easier to drill and tap a Tufnol Spacer rather than the cast manifold, or just feed the breather into the airbox, on the engine side of the filter.

      Other possible use for a strong vacco connection used to be an automatic chain oiler, but maybe unnecessary in this case, there is plenty of oil around the chain " au naturelle" with the breather outlet pipe to the sump plate removed (early engines), short stub pipe later plunger, no pipe on S/A. Interesting to see if the vacco can connect to the breather outlet.

     Drain tap on tank is convenient, if that's what it is, but was a bit of a risk as regards unintentional operation.....messy, expensive and a  long push home.

 Swarfy.

[roys51a10]

Well i found the pipe that was on it.And it its just blanked off.My mother (Roy's wife) seems to think it had an air horn fitted! Googling vacuum air horn they did exist.There is 2 holes drilled in the carb 'ski slope' where it could have been fitted. I'm just going to screw a blanking plug into the manifold. Yes that is a tap on the bottom, possibly going to leave it there.