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twin carbs

Posted: Sun Feb 27, 2011 1:55 pm
by andrew.searston
hi everyone :D
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???

Re: twin carbs

Posted: Sun Feb 27, 2011 2:02 pm
by bmcecosse
Try Sprite instead of Coke ? :lol:
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 ?

Re: twin carbs

Posted: Sun Feb 27, 2011 6:44 pm
by andrew.searston
haha mean chock not coke :D
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??

Re: twin carbs

Posted: Sun Feb 27, 2011 7:41 pm
by 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 ??

Re: twin carbs

Posted: Sun Feb 27, 2011 9:13 pm
by andrew.searston
i realy do mean choke, 3rd time lucky :D
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????

Re: twin carbs

Posted: Sun Feb 27, 2011 9:17 pm
by 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......

Re: twin carbs

Posted: Sun Feb 27, 2011 9:52 pm
by 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]Image[/frame]

Re: twin carbs

Posted: Sun Feb 27, 2011 10:01 pm
by 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 ?