I’ve forgotten just how long it’s been since the List discussed the
“Throttle Spindle Levers” but since it has come up again, I thought I’d
offer the fact that the 120 Parts Book, pages 13 to 14D and Plates D and AD,
both show two (2ea) “Lever on Throttle Spindles”. The part numbers appear
the same for both the early and later models, but the plates illustrate that
the later style lever (Plate AD) was separate from the idle adjustment.
For whatever reason, many 120’s apparently did not have the second lever (on
the front carburetor). In our earlier list discussion, it was reasoned that
a lever and return spring on the front carburetor was desirable to hold that
carburetor against its idle stop when making individual idle adjustments.
I have personally observed that (when present) some of the levers for the
120 front carburetor are slightly shorter than those for the rear, since the
longer levers may not clear the starting carburetor. The return spring, for
the lever on the front carburetor, was attached to a short stiff steel strap
as Joel described a couple days back. The 120 Parts Book likely never caught
up with whatever service change introduced the support bracket.
However, the XK140 Parts Book gets the whole configuration straightened out.
It illustrates, on Plate H, the “Bracket, anchoring return springs” and
lists on pages 25 and 27 the different levers, part numbers, etc.
Both of my 120’s only have one lever (belcrank) for the return spring.
They are located nearest the bulkhead and the spring hooks traditionally
to the brush cover band’s clamp screw on the cranking motor.
I’ve re arranged this rather “one sided” affair by relocating the lever
between the carbs and fastening the spring to a piece of metal strapping
that is bolted to the left corner of the oil cannister top casting. I
put a 90 degree twist in the strap, so as to, make changing the filter as
easy as possible.
We have much discussion (First Tuesday gang) about the wear caused by
this “pull down” arrangement regardless of where it might be located and
have come to the conclusion that coil springs around the shafts would
have been much better and would minimize “egging” of the castings and
vacuum loss
We have also discussed simple ways of externally sealing the shaft to the
casting using simple coil sprung, washer faced, greased felt gaskets,
that in theory, seem effective…the internal clearance around the plate
at the pivot is another matter as no one seems to have addressed it with
anything but conjecture.
The jury is still out, but IMHO it is a bit easier to adjust the throttle
plates to the screw stops with the return spring in between. I have a
few assorted SU levers, but none quite match that on the 120, therefore I
have not tried two (at least yet). The original `120 levers seem longer
and more delicate than my spares.
I’m still breaking the engine in and haven’t quite gotten to “tweaking”
it, so a lot of the finessing is still to come. Right now, keeping it
together is topmost.