float chamber vent valves more observations

[sujitroy]

I also have a set from a Fed '73 sitting on the bench too. My current '71 Stag has a pair of carbs from a UK '71 Stag which suffers
from hot starting issues. Based on another thread and a reply from Tony Hart he says there could be problems with the float chamber
vents.
There was a change on the lever mechanisum on the '76 carb set. ( from LF 42914) With no throttle, the lever of the vent valve is fully
pressed home which alows the float chamber to fully vent to the atmosphere. If you blow through the vent pipe, you can feel air
coming out of the fuel intake pipe.

Lets assume the float chambers are empty, you turn the ignition on, the pump starts
ticking and the float chamber begin to fill with fuel. In this case, the air in the chamber can vent.

On the '71 set as well as the Fed '73 set of carbs., with the throttle closed the lever is floating so the vent could be
partially open or closed. In my case with the no throttle, you can't blow air through the vent pipe. It is blocked.

In this case, lets assume the float chambers are empty, you turn the ignition on, the pump starts
ticking and the float chamber tries to fill, but because the vent is blocked, the air has no where to go, the pump stops ticking. and
no fuel gets into the chamber.

Does this sound plauable?

Here are some photos.


Sujit

[trunt]

My understanding is that the vent valves are not “closed or open” but rather venting to one place or another.

Cant remember where I got that from but I’ll look!

Terry

[trunt]

Yes, it vents to the air filter when throttle is open, to the carbon canister when throttle closed. so check both paths..
Not sure on the 76 but the linkage looks to be doing the same thing, pushing the vent valve when throttle released?

here:- good old Buckeye site.

http://www.buckeyetriumphs.org/techn...bsI/CarbsI.htm

However:: When I did my 71 carbs I actually removed the valves and cleaned/checked them, BUT they say that is post 73 (TR6), plus it shows the newer lever arrangement.

Mine came from a 71 and have the same lever arrangement as your 71 picture but it definitely had the brass thingy, had to tap the brass hole to the air filter and use a bolt to extract it, as per their instructions.

I also remember blowing down the pipe that goes to the carbon and it blocking when the throttle is OFF the end-stop.. going to do that again now

[trunt]

OK, No smutty remarks please but..

When I gently suck and blow on the pipe sticking out of the carb at 90 degrees to the inlet face (the carbon canister pipe) with the throttle closed its free, air flows.
when I open the throttle its blocked (well almost)

When I gently suck/blow on the pipe coming out of the inlet elbow (air filter) it is blocked when throttle is closed, open when throttle is open.

This corresponds with the theory on the Buckeye site

As its moving from one to the other they both get very free, but thats due to them both being open for a little while and is not important, probably why you mentioned it "floating"

Terry