Acceleration 3rd & 4th

when you're driving in third gear, and drop the revs to change into fourth, the carb is hardly open...there should be a small black pipe that connects from the "flying saucer" on the side of the Dizzy, to the carb...this tells the ignition system what to do...as soon as you put your foot down, the carb opens up and the "flying saucer" stops what it was doing.
Two ways to test it: With the engine OFF
1) disconnect the black pipe from the carb and suck on the pipe....you should hear a clunk in the dizzy
2) reconnect the pipe to the carb....disconnect the pipe from the "flying saucer"....start the engine but don't rev it at all....the pipe should hiss

If either of these are at fault, you'll experience the symptoms you're having

 

Yeah, you need to be doing over 40mph in third before you go into 4th

 

As someone said earlier, depending on conditions change from 2nd to 3rd at 25mph and into 4th at 45mph. Even then it'll take a while to build up speed in 4th, but that's as good as it gets. A 1600 in tip-top order isn't so bad, but still fairly uninspiring.
Twin carbs will improve it.
And so will many other mods to the engine.

The worst place to drive a 1600 is around Milton Keynes because every time you get up to a reasonable speed there's another bliddy roundabout.
The second worst is Wales - all those bliddy hills!

 

It's an alternative place to get a vac signal for the warm air flap in the air filter.

 

I like that. lol

 

thank you so much for all your wonderful responses, i'll take her on the M4 tomorrow and let you know how I get on, @poptop2 do I need to replace the pipe that's been sealed? if so whats the correct term so that I can order it?
thx

 

Not all manifolds are the same. They have different spurs, some have a 12mm for servo, some a 2mm vac signal, some both and some none at all. That's why you see a variation in things that need vacuum plumbing. All apart from the distributor which needs a varying signal from a specific part of the carb.

 

Don't mean it's workin' though init....

 

Hey @zed ...while you're there....do all 3 and 4 manifolds have a flat casting in between for a servo take-off, or did I dream it?

 

I will replace the breather and filler cap

 

I didn't say that. There should be a small vac pipe from either your blanked off carb pipe, OR from the inlet manifold an inch below the carb on the left side, to the top rear or your air filter box where there are 2 connections. The other is connected to the disc-like part of the air intake nozzle. This is assuming everything I'm advising connecting up actually works.

 

twin port manifolds? It looks that way but I've never seen one drilled and used.

 

is it possible someone could download this pic and photoshop where the small pipe or hose is supposed to go please

 

so the little "hole" in the mid of carb is where a pipe is supposed to be?
if yes whats the terminology for it and where does it connect to