Hi 
  Im pretty much a newbie so all help would be much appreciated. Ive purchased a 2002 Sherco 290, got it fairly cheaply. Stupidly i didnt go to see the bike as i bought it from ebay and sent a friend with a van to pick it up.  
 Two problems - firstly the engine has a knocking/tapping noise which increases with revs, it is fairly loud but the bike dosent seem to be down on power or smoke more than it should. any suggestions?   
  Also when i rev the bike, either in neutral or in gear, when i let off the throttle the revs seem to stay up for a short while then eventually drop back down to tickover? 
 Really not sure what to try so any suggestions would be great! 
 Many thanks