SU problems (I think)

[Robert Leigh]

I find that the best cleaning fluid for the working parts is methylated spirits, with which I use an old toothbrush until the piston and dashpot have no signs of dark marks. Then check that the piston rises and falls with no trace of a scraping noise between the piston and dashpot. The piston should move freely by gravity and covering the top of the dashpot with your thumb should cause the movement to be considerably slower as air has to be admitted past the piston through the small circumferential clearance.. Gritty noises are unacceptable and dashpot and piston can be cleaned again if this happens using a lint free cloth with methylated spirits. Only after getting this bit right is it worth experimenting with different needles, damper or no damper, etc.