Okay im not very mechanically minded at all but unfortunately my sisters fiance has bought a caravan and quite thoughtfully parked it in my driveway blocking my path to the garage so I've had to leave my bike out in the open air and rain. So anyway, I had been taking the car for a few weeks and left the bike out there for about 2 weeks and after cleaning the cobwebs on a good day I decided to take her for a ride but when riding, it seems to choke when it hits certain speeds like 40, 60, 80 etc. then it rides through it till the next choke point. My friends said its either dirty fuel or something burned out, can't remember but does this sound like something a mechanic needs to deal with? I'm quite poor so want to avoid trips to the mechanic at the moment.