idle speed drops in my 309

Hi. I have problems with idle speed recently. I have TU 1.4 carb engine.
Carburator has been rebuilt recently. When I stop at traffic light idle
speed stays at 900-1000 for a few moments and then slowly drops until the
engine finally dies. It happens regardless of engine being cold or hot,
although when it's cold and I close the choke (manual) it happens less
often. Strangest thing is that when I step on the gas the engine first rev
down slightly (200-300 rpm) before reving up. Does anyone know if this
strange behavior indicates something?
Thanks!

 

Float chamber needle valve not seating properly - fuel level gradually
rises when idling until mixture becomes too rich.

Ron Robinson

 

Thanks Rob. What confused me is that when I closed the choke (which made the
mixture even richer) the idle speed somehow stabilized. I would assume that
this should cause the engine to stall. Could it be the other way around,
that the mixture becomes too lean?

 

CHECK YOUR FLOAT LEVEL IN THE CARB ALSO IT MIGHT PAY YOU TO FIT NEW FLOAT AND SEAT PLUS NEDDLE .GOOD LUCK.SORRY FOR CAPS AS MY KEY IS BROKEN,FROM CHRIS ADDLESTONE SURREY

 

Sorry, I took "closed the choke" to mean "pushed the choke knob in".
However operating the choke usually does two things: richen the mixture and
increase the idle speed. If there is a slight leak past the needle valve or
the float level is too high, pulling the choke out will result in using more
fuel thus stopping the fuel level rising so fast and the increased throttle
opening will also help to keep things stable.
Anyway, if this fault appeared when you fitted the different carb., see the
people you got it from. - it's their problem.

Ron Robinson