The spring and plastic part should be removed,
leaving only metal parts on the main body and the
top cover. I used carburetor cleaner to remove all
the grime, followed by acetone, but any good
solvent should work.
Once most of the dirt was removed, I lightly sanded
the inside of the primary chamber with 400 and then
600 sandpaper, followed by a 1500 grit automotive
rubbing compound. A final rinse with acetone made
the parts squeaky clean.
The plastic parts shouldn't be put in the solvent,
but they need to be clean none-the-less. I used
regular soap and water for this job.
There is an air-filter on the intake....
....and a plastic rocker, both of which should be
removed and set aside.