twin carbs

[andrew.searston]

hi everyone
i own a mgb gt with twin carbs. its running rough and i have to drive with the coke out slightly other wise it cuts out
its also hesitates and splutts
could this be timing or carbs???

[bmcecosse]

Try Sprite instead of Coke ?
And the answer is - YES - it could be either carbs OR ignition. So you have to go through the usual checks - valve gaps correct? What colour are the plugs ? Are they good condition/correctly gapped. Engine compression check ?

[andrew.searston]

haha mean chock not coke
ive set the valves, and the guy i bought it off has just replaced the spark plugs so their clean.
do you know why i have to drive with the chock partly out all the time??

[bmcecosse]

Can only assume it is very weak - and CHOKE by the way! Are there any obvious air leaks into the manifold? Servo hose leaking perhaps? Closed circuit breathing system leaking - does it have the 'PCV' valve ??

[andrew.searston]

i realy do mean choke, 3rd time lucky
so by replaceing inlet manifold gaskets and exhaust (just to be on the safe side) might cure the choke problem as it does have a hissing sound round that area.
and whats a pcv valve????

[bmcecosse]

I think it stands for Pressure Control Valve and was fitted to some models (Minors also) to ensure the crankcase gases were sucked into the manifold and burned - except not when idling. If the diaphragm in the valve fails - you get the symptoms you seem to have......

[andrew.searston]

just had a look and i dont think it has a pcv
but it does have a vac pipe coming from the servo to the inlet
heres a pic[frame][/frame]

[bmcecosse]

Agree - I don't see a PCV . So can only suggest you check for air leaks. Do the carb pistons rise and fall easily ? Is there oil in the carb dashpots? Are the carbs well syncronised ?