Had a 2008 250f for a couple of years, the best bike I have ever owned. My son wanted a bike so I treated myself to a brand new factory 250 on April 2nd. It has been a real dog of a bike. When accelerating through the mid range the bike bogs down. Sent back to dealer who kept the bike for a week. Picked it up on Saturday, it seemed better. Today the bike is improved, needle height lowered, and carb cleaned. I have put an iridium plug in it, but it still has a bogging issue. The bike is nowhere near the 2008 model. Is this a common problem, is it cos the engine is still tight? Lost faith in the dealer, any suggestions gratefully received.