on four wheeler engines pressure washer to get big stuff then soak it in toilet bowl cleaner , then wash again , that toilet bowl cleaner will pull some stuff off.
On saws , scrape the big crap , then put it in parts washer , got a set of various sized wire brushes. one big like for grill , one medium then a samll one like a tooth brush , ( p.s. deisil works in parts washer just fine ) and scrub and scarpe until i got it clean as i want it , i do the cleaning primarily when i got the saw bout tore down , leave cyliner on it to keepo garbage out of crankcase .