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MG MGB Technical - BGT is fouling plugs


I have a '74 BGT that keeps loading up at idle and fouling the plugs. The mixture adjusters are pretty well leaned out, so I suspect that it needs new needles. Any other suggestions?

The alternator is also not charging (ignition light stays on). Connections are good. I was wondering if Lucas alternators can be repaired easily or if I should just look for a rebuilt one.

Thanks in advance.

Dave
David Plantz

Had the carbs off lately?
Dan Robinson


Hi Dan,

No, I haven't recently pulled the carbs. They're not leaking fuel as of now though. Since these are HIF 4's, the throttle shafts feel pretty good as well.

Thanks,
Dave
Dave Plantz

Dave,

Carbs are rarely the problem, unless needls do wear. I think the way the HIF4 is set up this isn't likely. I would set my valve lash first, than do a compression test, and then check my timing. If you take out a spark plug and rig a spark tester, you should be able to make the spark jump about 7/16" in ambiant air pressure. If not, check the resistance of your wires, and the inside of your distributer cap for arcing. Replace your rotor, check your coil.

I'm assuming that you can turn your engine over on the battery, if so, it probably has enough coil spark to run, but that spark jumping test is doubly important.

There is a Saturn Alternator which practicaly drops right in, more power, easier availabilty and cheaper. you might want to search the archives on that.

good luck,
dave
Dave Braun

Carbs should be the last thing to be adjusted, so as Dave says go right the through the valves and ignition before setting up the carbs from scratch for air and mixture balance and flow. HIFs also have a separate enrichment valve so make sure its cam is fully closed, but even then the valve is internal so could still be leaking. The HS arrangement is more convenient, at least.

Lucas alts can be repaired or exchanged, the latter would normally be preferable as everything should have been done and checked, but many report problems with rebuilds, it all depends on the ethics of the rebuilder.
Paul Hunt 2

As above, rule of thumb is 90% of all carb problems are electrical. That said - I've had trouble after storage of carb needles getting a varnish or coating, which ends up blocking the seating orifice in the carb, preventing idle and smooth running. Look at the needle when the car is trying to run and see if you're getting a good "spray" from both carbs. If the needle is crudded up (looking reddish brown and not shiny brass), at idle one or both carbs will not carburate cleanly.

Carefully remove the carb "bell", don't screw up the spring and lift off the internal casting, again taking care not to drop or bend the needle. I used the finest sand paper I could find and gently cleaned off the needle(s). Re-assemble.

John Z.

This thread was discussed between 15/04/2007 and 17/04/2007

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