Last I checked, just about any oil that gets burned during combustion results in carbon and/or ash deposits. Kind of a given.
I don't run those YS jobbies... not my cup of tea; but the 4-strokes I do have only have a very light film of carbon on the exhaust valve and that's using 20% all castor oil in the fuel. I probably have 3-4 gallons through one of them. Not a spec of anything on the piston.