> The jet centering 'pin' doesn't fit in the jet - its too big.
Frankly, I found even the genuine SU centering pin to be somewhat less than
effective. Even after aligning with it, I found that the needle rubbed the
jet hard enough to affect piston motion. Not sure exactly what the problem
is; but I can see at least 2 potential problems with the basic design :
1) It assumes that the needle runs concentric with the hole in the carb body
... if it was all machined that accurately then there would be no need for
jet centering at all !
2) The SU jet centering pin is a very light push fit into both jet & carb
body; which means several .001" of clearance ... enough to allow significant
misalignment.
What works for me is to remove the mixture nut and push the jet all the way
up. Then fiddle with the jet housing until the needle fits cleanly into the
(higher than normal) jet with the clamp nut firmly tightened (tightening the
nut seems to always move the jet a bit). Then pull the jet out, reinstall
the mixture nut and spring, and reinstall the jet.
This uses the base of the needle itself as the centering pin, so no question
of machining tolerances stacking up; and having the jet higher than normal
ensures there is actually some clearance with the jet in normal position.
YMMV of course, but I've used this technique many times and on several
different TR3/As; works for me.
Oh yeah, I got a genuine SU tool kit from JC Whitney over 30 years ago ...
they don't carry them any more <G>
Randall
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