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MG MGB Technical - gremlins

Ladies and gents; If anyone can figure this one out I don my hat to you. I just obtained a pristine 1974(july) B. everything is immaculate. Still have the original paperwork from where it was bought in Honolulu. Runs great etc. EXCEPT; In the morning; Pull out choke, start engine, return choke to running position when ready. All is well, engine purring. Take off down the street. At the same point every day the engine starts to crapout. Acts like it's flooded. Lasts about twenty seconds then is fine for the rest of the day. I figure it's menehunes or leprechauns or such. Any ideas?
Joel

Joel, in sounds like your car is running rich, as though the chokes are still operating for a short time after the choke knob is pushed in. Check the choke return springs. On the HIF carbs the choke mechanism is a rotating disc (I think) on the side of each carb. There is wound coil spring next to the disc as well as the long spring on the lever mechanism. Check that both springs on each carb are in good condition, and returning completely when the choke knob is pushed fully in.

Also check that both carbs are synchronized and operating correctly.

Andy 67 B, 74 GT
Andy Preston

Maybe fuel pump?
Lewis

Try applying the choke when the engine hits that bad spot. You may need to have the choke on a little longer. If it gets worse with the choke on, let us know.
Jeff Schlemmer

Jeff may be right, and if so, you would make that screw adjustment at the choke cam if an HIF has one (I forget). You would only need to make a small/slight adjustment as the choke cam adjustment just changes the point at which the choke goes out of use as you release the choke cable. You may only need to get it to shut down a little later (at a point a little closer in to the dash on the cable run).
Bob Muenchausen

We've had a couple of these in the past, the last one going over Sydney harbour bridge as I recall, didn't see any fix.

HIFs do have a fast idle cam and screw on the choke spindle just like HSs.

I'd take out a plug to see if it *is* flooded, or you could be chasing a Will o' the wisp instead of a gremlin. It also sounds like you are starting the car and warming it up before driving off. You shouldn't really be doing this, it is better to drive off immediately after starting, pushing the choke back progressively as you go. Even if you still warm it up before driving off the choke must still be pushed back progressively as it warms, or you will be running very rich, washing oil off the bores, and causing rapid engine wear. The choke is a continuously variable control, not an on/off switch.
Paul Hunt 2

Joel,
The fact that the car starts to run poorly at exactly the same place indicates to me that one of your carb floats is sticking closed. You're running on both carbs until one of the bowls is drained. After sputtering along for a while, the float opens, the bowl fills, and you're on your way. I've found that Grose jets are extremely prone to this problem. Change them back to stock jets and the problem will go away.

John
JFR John

Thanks guys; John, I think you may be onto something. It does act exactly like a stuck float. The car sat for two years until recently. Things are a bit sticky. Will keep you posted after I've had time to dig into it a bit. I've got a back-up pair of HIFs. May be time to rebuilt them and throw them on.
Joel

This thread was discussed between 19/11/2005 and 21/11/2005

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