Peugeot Speedfight help!!!

hi everyone
ive got a speedfight 2 Air Cooled 2005
yesterday i noticed when i let the throttle off the revs arent going down or when they do are taking a long time to go down so the bike is staying at a lot higher revs.
my dad said it sounds like there air coming out of somewhere but we've checked the manifold, carb ect, and theres nothing that seems to be wrong so just wondering if anyone knows what it could be?

any help will be much appreciated
thanks brad

 

does it bog at top end

 

no but it isnt going as fast

 

it sound like an air leak could be your crank seal is on its way out

 

could also be a sticking throttle, cable sticking, sticking carb slide or frayed cable...or an air leak. Have a look around the rubber inlet manifold too as they crack

 

I was going to say sticking throttle, Have you tried cleaning all your carb and the throttle pin etc?