That's a good question....
Motorrad has helped me tremendously on this.
It also helps if you have another cylinder or two to compare with...
If there is a big wad of rough jibbly gunk on one cylinder but the other 3 stock cylinders don't have it, I think it's a safe bet that it can be removed.
Then again there is always the exception to the rule....
If your not sure, better leave it.

