G'day mate,
Glycol (antifreeze) in an OLD crockpot, strip engine, & cover with glycol, crockpot on low heat, for 24 hours, will clean up nicely. Don't put anything in the crockpot that has rubber on it, gaskets & so on.
& NEVER EVER USE crockpot for cooking food ever again, glycol is POISONOUS & will kill.
Also the fumes are dangerous too, so use in well ventilated area.

And use synthetic oil, in your fuel & the problem goes away. That will get em goin!!!!!