Carbs on startup

[Peter Douglas W]

Here is a nice one for the experts.
If I start my carb (175CD-S) Triumph with the choke everything is OK.
If I start without using the choke (which is possible) it has the symtons of running weak (not suprising). If I then pull the choke out to richen the mixture it does not change this weak effect. I just have to wait until the car is warm. Why?
What does the choke do or not do inside the carb, to cause this effect?

[Clifford Pope]

Just a suggestion:
<br>the first bit of movement of the choke turns a cam lever which opens the throttle slightly, to give a faster idle, as well as enriching the mixture. If you pull the choke without opening the throttle at all, the choke cable and mechanism have to pull against the throttle spring too. If you open the throttle a bit and then pull the choke (as I do before starting from cold)then the cable only has to activate the choke. So maybe stiffness or play in the linkage somewhere means the choke doesn\'t always respond to the same extent for a given distance of pull at the knob.
<br>Another idea might be a bit of sticking from the carb diaphrams. When starting on the choke mine gives a satisfying roar as it fires up, and I then ease in the choke to get a reasonable idle. Maybe this initial burst loosens the damper assemblies. If on the other hand it starts rather limply, without choke, this effect is lost.