I am not making any comments or expressing my opinion, in fact, I use Amsoil 20W-50 and am very happy but I did find this thread on HDforums.com, rather interesting

http://www.hdforums.com/forum/touring-models/544755-amsoil-experience.html

Read the replies, They Are for Amsoil, You can't take one story, it may be a poser trying to sell another oil.
Oil wise, amsoil got us where we are to day in synthetics, and I know they make special oils that they formulated just for certain Harley's.

He could have put wrong stuff in, and who knows whats up with his bike. But I personally had Amsoil in with over 8K miles on that oil and filter and got stuck in a traffic jam in over 100 degree heat and it ran fine, I only changed it because I know how hot it got moving up 3 feet at a time. Jam, left running, no air, heat humidity, every oils nightmare and after I changed it, I was sorry I didn't run the trip out with the Amsoil as the Mobile One made it run louder.

I hate amsoil because you can't but it OTC But I doubt anyone makes better oil.

I just found the whole thread interesting. I use it because I can get it locally and I run it 7-8,000 miles with a filter change at about 4,000. Works for me.

I can give you all the facts of my experience with Amsoil. I made a run from Corinth Texas to Oklahoma City and back this past weekend in triple digit temperatures running 85 and 90 the entire way up and back. I had Amsoil 20w 50 in my engine and Amsoil Severe Gear in my transfer case. The bike ran strong and never missed a beat. No issues with overheating or un-natural engine noises whatsoever. The temps were so severe it felt like I was in a convection oven riding down the super slab. It was brutal heat and Amsoil performed flawlessly as did my bike. On the other hand, one of my brothers HD did overheat and in fact lost oil pressure to zero when we went to leave a rest stop. He had Synthetic oil in his as well, but I don't know what brand it was. In all fairness, he has had issues with oil pressure and overheating for a while now. I don't know the circumstances of the issue in the HD forum listed in the link of this thread, but If I can run in triple digit heat at 85 and 90 MPH the entire trip up and back, I would say that Amsoil is not the problem he was having in the "high 90 degree heat" he said was riding in. BTW, the Amsoil in both my engine and transfer case, as well as my Mobil 1 oil filter have 8000 plus miles on them.

I'm neither for or against Amsoil but that guys story sounds like a whole big helping of crap. No way do you maintain good pressure if you're running low viscosity oil like he described, pressure would drop right off. And, for the engine to make that much noise and for him to still ride it to a shop and have no damage?? C'mon........

That almost sounds like the gas/oil problem the old Yamaha XS750 & 850's had. The petcock would leak, if the bike was on the side stand the carb would flood and the gas would run right in to the engine oil. I know the Amsoil is a good product. Most likely the Harley had a leaky petcock and the carb flooded.

I have the Amsoil 20W50 in my bike now, and I have more engine noise than when I was running an el'cheapo 20W50. I'm not saying the oil is bad or good, that is just my personal experience from running the oil. Next time I do an oil change, I will be going back to the cheap stuff and just change it twice as often.
And on the third page, there's a poster by the username of Bearcat1 who reports he had the same problem.
Edit: There's another poster on page 5, username BLKBAGGER, and page 10 with user lonerider,

I've never really had a problem or reason to steer away from Dino oil. Maybe the difference in time you can run the oil might make a difference. I personally change the oil 2 times a year. Fall and middle of summer sometime in July. Thats just about 3 thousand miles for me. I would not feel comfortable leaving oil the in for a year Just force of habit I guess.

Although if I was going to put a ton of miles on in one trip I would definately go with the synthetic.

HD has had problems on certain years with the rear jug leaking and pressure loss. I have read that for certain engines between 2006 and 2008.

Like one of those posters noted:

It was likely something else - such as filter. And starving upper end for oil in that heat it was a damn good thing he had quality product like Amsoil in there or he would have had a major rebuild to deal with