First use anything non-petroleum that is made to loosen up sludge, rinse it out and try again.
I was cleaning one for weeks then realized it was impacted badly. I tried kerosene, it helped a little but not enough. I put it in a old washing tub outdoors and away from anything that would catch fire. I got the tube hot with a propane torch. The sludge self ignited and burned itself clean (white inside). It sounded like a small jet engine. It belched a lot of black smoke and I suspect it was toxic. Be careful if you try this folks. Hours later after it cooled down, with respirator on I blew it out several times with an air hose. Then I sprayed some lube inside to keep it from rusting then wiped the exterior down with lacquer thinner. Primer and paint then reinstalled. The engine ran better.
I got lucky with the sequence. Right after cleaning the draft tube, I replaced the valve cover and lifter oil galley cover gaskets (the traditional way, including flattening the sheet metal). Hey! The oil leaks went away. Only a slight weep typical of all cork gaskets.
Will the draft tube sludge up again. On an engine with worn piston rings, you betcha.
Last edited by buoymaker; 08/15/2022 7:34 PM.
