I would suggest that while you are stripping the carb. to clean it that you also fit a pump diaphram and valve set.
Watch out for the needle valve and lever when taking out the pump diaphram, as on some types of carb. there is a mushroom headed pin onto which the needle valve lever is attached by a forked end.
Dismantle on a clear bench or table covered with clean cloth. This will help you find any parts you drop.
If the mixture screws have been moved the usual basic setting is one and a half turns open, then fine tune when running.
J. Beaver, October 2008