just serviced mine and it was a pit of black oil and sludge. Washed everything in kero before I started to dismantle the unit. The dowl pins on mine were also stuck so I washed all the gunk from around and under the slides and pins and used compressed air to blow them loose. Watch your eyes as cleaning fluid sprays everywhere. Your mileage may vary but this worked for me.
Hope this helps mate.
KJ