Motorcycle Repair: Synthetic versus regular Oil, friction modifiers, petroleum based products

Question
Hey Wayne, I have a 99 1100cc , air cooled Yamaha Virago with about 40,000 kilometres. Is there an advantage of me swtiching to a synthetic oil such as Royal Purple or Ams? Also is one better than the other? My owners guide says for normal weather temp, use 10w30.

Answer
Mark,

no huge advantage to synthetic and I am not
sure if they contain friction modifiers that
could impair clutch operation. If it says
"for motorcycles" it might be okay.
-The synthetic may be good for keeping
hot spots lubed due to it's molecular
constituancy. It seems that most test results
favor Amsoil overall but most top brand names are
very close.
I like using 10W40 unless your weather
is always cooler. These engines are mostly cooled by the
oil after-all.
I have found that some engines seem to run better
with the oil they originally were made to use.
I often go back to petroleum based products
if things don't seem right while running
synthetics. It's okay to switch back as most of these
oils seem to mix okay.
Note: The improved solvency of synthetics can clean
out oil deposits which can expose a poor oil seal
causing it to start leaking. (info from Royal Purple)