my gilera cougar loses power when u go into to 5th gear?

well it sounds like it is just running out of power to me ,it could be that its low on compression for some reason possibly a leaking valve as you mention but could also be a worn piston and bore.has it always been like this or has it got bad lately?you could try fitting a smaller front sprocket to the bike they are only a tenner and give you more acceleration and would help with your problem.only go down 1 tooth though the standard one is about 15 teeth i think so you would need a 14 tooth front sprocket

adam bike doctor
September 2006