While it is almost unavoidable to get Castor stains on engines, you DO need to be aware that stains can point to a problem that newbies tend to overlook...

Namely that cap screws tend to loosen when the engine has been run for a while.

That lets the castor seep from the engine/cylinder head and other areas.

If you see castor stains on your engine you are advised to run the engine until warm, then remove one cap screw at a time, put thread lock on the screw ( after cleaning ) and partially re-tighten them down. Then torque them back down evenly alternating screws to get a good seal.



The engine should NOT continue to produce castor stains unless you spill fuel on the engine itself.


So DO pay attention to castor stains, they may represent a problem you may have overlooked.