For what it's worth, the original SU's on Triumphs were always the type
that had the fuel feed through the base of the float bowl into the
housing that carried the jet. The float bowl was attached and sealed
with rubber bushings. Earlier versions were sealed via a set of fiber
and brass washers. The SU's in which the fuel went into the bottom of
the jet via a small tube were used on Volvos and others. I don't
believe they were ever fitted to any Triumphs. However they worked fine
on Triumphs, and many folks would swap, because the chokes worked more
easily, and it was less difficult to rebuild.
Cheers.
On Tue, 18 Jul 2000, Trevor
Boicey wrote:
>
> > I turned the adjustment nut one flat up (leaner?) and
> > found to my suprise that the nut was virtually at the end (fully closed) of
> > it's travel.
>
> A few people alluded to this, but I thought I'd mention it.
>
> On the old "H" carbs, the jet bottom is a brass fork, that connects
> to the choke linkage. On other carbs a fuel pipe goes here, but on
> these carbs the fuel flows in elsewhere. Is this your carb?
>
> Another "gimme" for identifying this carb type is that the float bowl
> lids
> are held on by one whitworth nut on top, instead of several slot screws
> around
> the edges.
>
> Anyways, open the choke, and look between the adjusting nut
> and the brass fork. You should see some of the jet in the space
> now, it looks like a length of 1/4 inch brass rod.
>
> Now release the clutch. You should NOT see any of this rod
> any more, the fork should butt right up against the adjusting
> nut.
>
> If you see any rod here, likely the jet is binding.
>
> Another test, remove the three screws and gently remove
> the suction chamber. (the top bowl thingie with the dashpot).
>
> Look into the hole, you should see the jet inside the jet
> bearing. Pull the choke, and you should see the jet drop
> down, release the choke and it should come up.
>
> The jet SHOULD come up pretty close to level, within
> 1/8th inch of level or more, especially with the carb adjusting
> nut all the way lean. This is actually what you are setting
> when you adjust the nut, how high the jet comes in it's
> sleeve.
>
> Anyways, back to a likely problem, if the jet doesn't come
> all the way up when the choke is off, again, the jet is binding.
>
> Most of the time you can get the jet to unbind by just
> centering it again, which is easy.
>
> Put the dashpot back on, and screw the three screws on again,
> we are done in there.
>
> Above the jet adjusting nut is a spring, at the other end
> of that is a slightly larger hex nut. Loosen that net a turn
> or so, until it starts to feel loose. Also, raise the jet
> adjusting nuts as high as they can go.
>
> Reach underneath, and slide the jet up and down, use the
> choke linkage as leverage if you need to. It should now
> slide easily, all the way up to where no rod is visible between
> the brass fork-thing and the adjusting nut.
>
> If and when it slides easily, hold it there and tighten the
> large hex nut you loosened a turn. Then see if it still rides
> smoothly.
>
> If it does, then you should be ok to tune up.
>
> --
> Trevor Boicey, P. Eng.
> Ottawa, Canada, tboicey@brit.ca
> ICQ #17432933 http://www.brit.ca/~tboicey/
> "What a brave corporate logo!"
>
James A. Ruffner
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