There are two problems with Castor oil.
If left unused in an engine it turns into a jelly like substance, presumably linked to it being hygroscopic, which is not easy to get out of nooks and crannies or oilways meaning an engine strip down. Clearly this will depend on the mix ratio and what level of the oil is actually left in the engine once the lighter parts have evaporated. Nick's experience and the simplicity of many of these 'later' two stroke engines would suggest this is not a great problem. More complex designs of an earlier era of engine design using a lot of oil would be a concern. Such things as aero rotary engines for instance.
The second thing to know is that Castor oil is a carcinogen and linked to certain cancers, I believe, so while it is great to smell, it should be treated with some degree of respect. It is not banned because it is not used greatly partly due to price and partly due to the issue of cleaning the engines up after use. Also I think the sort of devices we have have fallen off the official radar.
'Innit nice to actually be allowed to play with a dangerous chemical for once? As Nick will tell you French Supermarkets happily sell Sulphuric acid, Chlorine, Acetone etc. Not only that it tends to be stored all on one shelf. I often wonder what happens if the bottles fall and break. The French still assume people have a level of responsibility for themselves and if you want to dissolve your sheep do not complain about it afterwards. Very healthy too after our nanny state.
