Hi, I've got a twin carb, air cooled, 2l, petrol T25 and have just noticed the flaps in one of the carburetor isn't springing back as it should. Does anyone know how I can tighten this up so it works as it should? Or if I need to replace it, is it easily done? I've attached a photo of what I mean. Cheers
This is your choke flap. It should open after a few minutes from cold. If it doesn’t open you may need a new electrical heater unit. Check whether the electrical bit gets hot. If not it’s had it. It it’s still heating up, pull the unit off (3 screws) and ensure the curled up spring like thingy is engaging. As a last resort you can leave the electrical bit off and the flap will stay open. Mine usually starts OK on one choke only.
It might just be that the choke flap mechanism isnt hooked onto the heater spring properly - there should be a pin poking out into the heater element that operates the flap or affects its position, and a loop in the end of the spring in the heater capsule. This loop should be hooked over the pin. You then should be able to rotate the capsule until the flap closes when the heater is cold. then lock it with the screws round the edge. When the heater heats up the spring (its bimetallic) , the spring unwinds a bit and pulls the flap open via the pin . Flap dropped down is best setting if the heater has failed : cold idle will be worse but running will be more economical than flap shut all the time which is choke on. In fact , even with the choke on, theres a vacuum operated mechanism that should pull the flap open as the engine revs and airflow increases. This is so if you drive with the choke on its only at idle and pootling the that the fuel/air mixture is really rich.
One point though is that if the choke flap doesn’t open, fuel consuption will increase massively (12 mpg for me), and the engine will be very smelly. Since this isn’t mentioned perhaps one flap is slower than the other and only needs adjustment.
