QuestionI recently bought this B and it has an after market Weber Side Carb.#45DCOE152. The motor starts strong but the idle is set extremely to high. I have adjusted the idle on the carb with no change. This is my first experience with a MGB and am kind of lost with this one.
AnswerHi Joshua. The MG Factory never built MGBs with this carburetter, although it was a popular modification.
You may find it useful to have an exploded diagram of the 45 DCOE 152. Go to http://www.racetep.com/weber/45DCOE152.pdf
The tickover is normally set at the throttle adjusting screw (part # 52). The idle mixture for each bore is then set by adjusting the two idle mixture screws part # 56, after which it is usually necessary to reset the tickover using # 52 again.
I am concerned that your tickover is VERY high at 3,500 rpm. This usually indicates an air leak, for example the two large O rings where the carb bolts to the manifold.
Another common fault is a split O ring on one of the idle mixture screws (part # 44).
*** Note also the air bypass screws (part # 26) ***
In the USA, some adjusters are factory set and hidden behind tamper-proof' plugs, and recently they have added all kinds of junk to comply with the latest emissions regulations. It is possible that your carb has a single bypass idle adjustment screw' near the manifold in the centre of the Vee, so that it can provide extra air to both air intakes. If you can see a brass plug with a screwdriver slot and an O ring just below the head, that is the cause of your troubles. I have only seen these things on downdraft Webers, but the symptoms you are having are typical of a wrongly-adjusted bypass screw.
Let me know how you get on.
