I run synthetic in my Fatboy and I switched my toy over to it and it started knocking (conn. rod) so I switched back but after reading this I think I'll give it another try

I would research synthetic oils extensively before blindly taking my advise.  Everything that I have posted is truth as I know it; however I will admit that taking mechanical advise from me is like asking a donkey for financial advise I am a and that is why I enjoy learning from this site.

I am an engineer by profession (not mechanical) so I claim to have the ability to learn and apply what I read and I have enough working knowledge about engines to form and opinion that I usually run by some trusted friends that know more than I.  My guess on your connection rod knocking would be that it may have a problem that is/was being hidden by the conventional oil deposits in your engine.  It is possible that the synthetic was cleaning out the crap and allowing the failing part to move more and make noise.  It seems like a similar to synthetic oil leaking when the conventional oil didn't simply because it was removing the deposits (clogs) in the bad seals.  Just my 

You might try SeaFoam that seems to get great reviews on this site, I tried it and was mildly impressed with the results.