Well if your sure it's the carbs... As has been said before, 90% of SU
problems is ignition.
You don't say what kind of SUs they are.
What you want to open up and clean is the float bowls. Pretty easy on an
HS, a bit more on the involved on the HIF (remove from the car).
Start, however, with the suction chamber. That's the top where the
piston connected to the needle goes up and down. Take that off, and
make sure that the piston goes up and down the entire height without any
sticking. Also make sure that the needle is not bent *AT ALL*.
Now, if you have sticking. The manual says, find replacements. Well,
those, of course, aren't sold. You might look on ebay for another set
that you can rebuild or pirate pieces from.
My brother told me back when he had his Datsun Roadster, which had
Hitachi copies, he would use 600 sandpaper on the inside of the dashpot
to allow the piston to work properly. I know how well that worked, but
the car ran ok. I have a spare HIF with that sticking problem, that I
could try. Manuals that I've read say the suction in there is picky and
you don't want leaks around the outside.
Once, you are satisfied the dashpot/piston/needle is working correctly.
You can move on. There should be oil in the middle of the piston for
dampening. Replace that. With what is a religious war. To sum that up,
same oil as in the crank case, only 10/20/30W, Marvil Mystery Oil.
Whatever.
You might check the throttle shafts for wear, but this symptom doesn't
really match that problem.
I would then check the fuel pump to make sure it's functioning well.
No leaks, good voltage from the wires, good connection. You might check
the fuel pressure at the carbs. 1 1/2 pounds I believe. Someone will
correct me if I'm wrong. :-)
Now go into the float bowl. Ensure that it is clean inside there, that
the needle valve or gross valve is not sticking that the float is not
leaking and that it is properly adjusted. A can of spray Carburettor
cleaner should do the job.
If it's really bad, you might need to soak it in some Berryman's
Cleaning solution. It comes in a gallon can with a dip basket. Works
pretty well. If you go that far, you're half way thru a rebuild.
Paul.
77B - rebuilt HIFs.
Tab Julius 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
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