It had to
be something simple! This morning I visited a friend's workshop, for some kind
of second opinion on the carburettors. And after coffee and vlaai we started
with a few checks. His verdict was that the throttle disc of the front
carburettor wasn't aligned properly. Which also meant that fine tuning had to
wait till this was rectified. After some more coffee and vlaai I headed home to
do some household shopping, after which I made myself comfortable to remove the
carburettors again to check the alignment of the throttle disc of the front
carburettor. Well there was nothing wrong with
the throttle disc. It was nicely centred and moved freely. But by the time I
found that out I already had found the culprit for the problems, this small piece of tissue
paper:
Rather embarrassing
really! While fitting the carburettors for the umpteenth time I almost forgot
to remove one of the gags of tissue paper I had stuffed in the two manifold
ports to prevent dust from entering. But with the front carburettor loosely in
place I noticed my error. So I just pulled the carburettor back a bit and pulled
the gag of tissue paper out. And I didn't notice that a small piece tore of and
remained behind on the two lower mounting studs, where it got wedged between
the carburettor flange and the manifold mount. And here, soaked in fuel and
preventing an airtight seal, it could provide extra air and fuel. But it could
also prevent the throttle disc from closing properly. Resulting in the problems
mentioned in the previous two posts on this subject. I knew it had to be something
embarrassingly simple!
With the
carburettors again in place it turned out very simple to set the idle speed at around
950 rpm. I won't set it any lower as the idle will become rather lumpy. This
being caused by the by now ancient Triumph Tune TT10204 Fast Road (280° duration) cam shaft
that is fitted to the car's engine. Hopefully I'll be able to fine tune the
carburettors within the next couple of days and see how the car runs now!
At least I am now again rather experienced in
removing and adjusting SU carburettors and have gathered a lot of knowledge on SU
working pressures, needle valve closing pressures, fuel pumps and so on. And I
have learned not to use tissue paper to keep dirt out, but to use cloth rags in
the future. But also to take my time to carry out certain jobs, and not rush them!
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