Motorcycle Repair: Smokin exhaust, suzuki gs750e, valve guides

Question
Hello,
I have an 81 Suzuki GS750E that I recently bought and when I accelerate there is gray/blue smoke that comes out of the exhaust.  The guy said that the engine was recently rebuilt, and the bike is in really great shape all around.  I just changed the oil and oil filter too. Also for this bike is it better to use premium or regular gas.
Thanks for the help,
Justin

Answer
Hi,
check your spark plugs, see if they are black=too much gas,
oily=rings or valve guides leaking, grey=running lean
or nice tan/brown=running good.
Could be it needs more miles to break in if the engine
is rebuilt or could be burning off old oil in the pipes
from bad running engine or old gas or badly seated rings,
Try taking it for a longer run and see if it starts
to clear up, put some fresh gas in, around 87 octane or so.
Hopefully it will improve :)