This symptom is consistent with a sticking needle valve. Here is what I have
done in similar circumstances. Remove the top of the float bowl -- the
dangling object is the float. Make sure it is not filled with fuel (thereby
not floating). Flip it up and down and observe the action on the needle
valve. Blow through the fuel inlet with the float in the up and the down
position, and you will get an understanding of how it works. Check the float
height as described in the manual. Remove all the fuel from the bowl with an
eyedropper or something similar, and clean out any remaining grunge with a
q-tip.
The float height adjustment is the only part of this that can affect
operation, so don't worry about "screwing up" your state of tune.
I have done this on the side of the road, discovering that the needle valve
had come "unscrewed" and had descended, jamming the float. Easily set right
-- later I went back and added some threadlocker to prevent a recurrence.
on 9/19/03 8:45 AM, Tab Julius at tab@penworks.com wrote:
> My '78B has twin SU carbs; I've been having intermittent (but always at
> inconvenient times) power problems; it more often than not happens on the
> highway when it's being given some gas. It falters, and slows, and will go
> like that for a few minutes, then will magically recover and be fine
> again. It seems to be a fuel delivery problem.
>
> I replaced the fuel filter; it originally seemed to make a difference on a
> quick test drive (about 10 miles @ 80 mph, no problem) except it faltered
> at the end.
>
> I then used GumOut, and the car liked the octane boost, but it wasn't long
> before it was faltering again.
>
> Now I'm looking at the carbs; I've no experience cleaning these (they've
> been on the car about 2 summer's worth). I unscrewed the top "bowl" or
> whatever it's called, on one of them, but it looked spotless inside. If I
> was to clean "gunk" out of the carbs, is this where it would
> accumulate? If so, I'll check the other one (I only wanted to fool with
> one at a time). I don't want to screw up the carb settings, so how can I
> safely clean them (or make sure they're not gunked) without screwing up the
> tuning?
>
> I can find articles on tuning them, but not on cleaning them... any
> suggestions?
>
> Thanks
>
> - Tab
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires
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