Motorcycle Repair: GSF 400 Bandit runs poorly at low revs, vacuum leaks, gsf400 bandit

Question
I have aqquired a GSF400 Bandit but it is running rough.  Starts on choke no problem but tickover is erratic. even when warm.  If you rev the bike it hesitates and then eventually pick up.  When riding if you open the throttle very slowly it is not too bad. Once you hit 8K revs all seems reasoanbly OK.  When you open the throttle when riding it almost seems to die before the revs pick up and the power surges in about 8K when it seem not too bad. Top speed is about 90mph whic is also down as well. I believe it to have a slight vacuum leak , or is it some more serious.  When over the 8K revs it runs not too bad.

Any ideas please?

Answer
Hi Bob.
 You may want to find out (if you don't already know) if the bike spent time in storage (seasonal or other).  If it did, then the carbs are probably gummed up a bit.  A good cleaning will be in order.

 Another possibility would be that the carbs are out of synch.  You should get that done.

 As far as vacuum leaks, it is a possibility also.  The way to test it is to start the bike and let it idle.  Then spray some ether (automotive starting fluid) onto the manifolds from as many angles as possible.  If the engine revs come up when you do that, then there is a vacuum leak issue.
 If it is an issue, then it could be a leak in the manifold itself, or the connection from the carb to the manifold could be loose, or the connection from the manifold to the head could be loose.

Start with those and see what you find.
Good luck and ride safe.
FALCON