I use to use break cleaner to clean all kinds of car parts and guns. Back home.
Over here in Japan I never know whats in them so I use it out side, but never in a runing engine.
That is a lot of yen for break cleaner, are they the realy long cans that are like 1/2m long?
Also,
I bought some soldering flux over here, and it is super toxic I never had a soldering flux that made my eyes and nose burn so bad from the fumes.