If it's a replaceable one, buy another.
If it's a sponge one, wash it out well in paraffin and let it drip dry, remember to add a few drops of clean engine oli and scrunch it up a few times to spread the oil before refitting it.
Phil.H
February 2010
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lawn mowers.