I installed the rebuilt carbs tonight and have found a problem that I spent
2-3 hours with to no avail.
The front carb piston (HS4's) falls into place with a "clunk" as it's
supposed to but the rear one does not. It falls slowly and will not seat
with the characteristic sound.
I couldn't get the jet bearing centered properly to where the piston would
fall nicely into place. I spent a long time trying to get it right with the
needle in. I checked the new needle for straitness and it looked like it
might be a tad bit off center, so I tried the old needle. It caused the same
problem. Finally, I tried out the new jet centering tool in the SU tool kit
to adjust the jet bearing placement and the piston seated soundly with it
installed in place of the needle. Tightened up the bearing. Put the new
needle back in and it falls into place nicely until I tighten down the the
air chamber. Then it seats very slowly. If I don't install the air chamber
screws the piston "clunks" very nicely. But upon installing the screws and
tightening them, I'm back to the same problem.
I remember when I had the carbs off the car during the rebuild that I spent
an hour trying to get the jet bearing centered on this same carb. I did get
it working properly when it was off the car, without using the centering
tool. The only thing that I've done since is install them and top up the
damper with 20-50 Wt. oil. I overfilled them so I dumped the oil out and
filled them again. BTW, in the SU rebuild video, Laurie fills the damper
with the air filters off by lifting the piston all the way up and then
filling the inner tube to the top. I did this and had way too much oil to
install the damper piston.
So the quiz question for today is: What's the problem with the piston not
"clunking"? Am I not holding my mouth in the right position?
Monte
79B, Carmine
67B, BRG
74 1/2 Rust, parts car
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