Ross.Vincenti@transamerica.com writes:
>Question - Has anyone (well, of course someone on this list has, that's why
>we are all members) rebuilt twin SU HS2 carbs lately? Any tips? I've
>rebuilt your basic American Holly and Rochester carbs, and once dismantled
>(note, I did not say "rebuilt") a Zenith carb on an early Bug. So, is an SU
>that much different from a big, hairy chested, dual stage, 650 CFM, 4 barrel
>Rochester QuadraJet with mechanical secondaries?
It's different - it's FAR simpler!
Total moving parts: about 4 (butterfly, jet (for choke), needle
valve/float in the float chamber, and the piston).
The only fairly normal problem beyond the most dimwitted mechanic is
worn throttle shafts (actually it's the body of the carb/bushings that wears
more than the shafts). If so, get them reamed and rebushed for circa $50? at
Apple Hydraulics. Unless you're a machinist don't try it yourself; they have
to be align-bored.
DON'T sand or polish the piston or dashpot (or swap them). They're
carefully set up with a small clearance, unlike Strombergs which have
diaphragms (which rip and tear). Don't bend the needles (at least not the
new ones).
Balancing them & tuning is a minor art form, but only a minor one.
Dr. Bobwrench took some carbs I had tuned on a 948cc sprite (though I think I
took them from a 1275 to start with) and dropped them on a racing GT6 - and
he didn't even have to adjust the mixture or rebalance them, he says. :-)
> Am I about to be
>embarrassed and humbled by a little tiny side draft carb with funky
>Whitworth fasteners (of which I do not one a single wrench)?
I don't remember any whitworths - not that there are more than about
4 nuts anyways. If you're humbled by an SU (outside of worn throttle shafts),
sell your LBC now. 1/2 :-) If you're worried, spend $15 (or whatever) and
get the Haynes SU book. Not that it's needed.
--
Randell Jesup, Scala US R&D, Ex-Commodore-Amiga Engineer class of '94
Randell.Jesup@scala.com
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