Outing a fraud @ CL is tricky as you drop yourself in an arena with a person that will most likely not admit that he/she posted the wrong information. and will most likely either ignore or strongly challenge your correction statement.
That's why I pretty much leave those alone when I really feel the person is lying about an item for monetary gain. Better to do it indirectly through the people who manage the site instead if that option is available. as they may have more "leverage" on the guy to have them correct their statements.
Only time I jump is to clarify information where a seller might go " I'm not sure, but this could be a Peugeot or a Motobecane......." or "I think something is missing from the bike as there is this threaded hole....". They usually appreciate the constructive comments that I can supply identifying bikes and components that the seller might not be familiar with and explaining their functiuons with more back up info, of course.
JMOs

Chombi