Originally Posted by
JohnDThompson
Grease is an emulsion of soap and oil. The solid matter you see is the soap component left behind after the oil has separated from the emulsion and drained out. If you want to avoid potentially toxic solvents to deal with this, try adding back some mineral oil and working it back into the soap. This can reconstitute the grease and make it easier to clean out with e.g. a rag.
Personally, that's more work than I am inclined to put into a job like this. I'd just use mineral spirits, nitrile gloves, a brush and a rag and be done with it.
Thank you for reminding one and all that grease is oil and soap. This is why after working with grease it is possible to clean one's hands with soap and water. OP was asking about how to do the job w/o resort to nasty chemicals (OP's phrase), soap and water are usually not categorized as nasty.
In the bigger hammer department nitromethane cleans most anything. Last I had a reason to contemplate buying some the minimum quantity was a 55 gallon drum and price was about $3000. Is that a problem? Just throw the whole bike in the nitro and guarantee by morning that's one clean bike. Do you want clean or not? I have it on good authority that the legendary Shelbrothane Chain Cleaner was nitromethane. Deakinol of course was 190 proof grain alcohol. Useful for many things. Then you could try an industrial pressure washer loaded with nitro. Or flamethrowers. Do not forget flamethrowers.