Dying due to air promblem or overheating maybe?

[Viirin]

I been having some issues with my GZ as of late - if i have a clear run for about 90 seconds at about 35-40 mph, the bike looses power and then the engine cuts out all together. The bike can't be started immediately but it can be after about 40 seconds but then the idle sounds very uneven and if it's ridden again, dies in about 100 meters. sometimes if i've got a fairly long run up to a set of lights i can hear the engine idling at about half of what it normally does and then it feels like a race to for the lights to turn so i can get going before it cuts out. - I thought the bike wasn't getting enough fuel but i checked the line and it seems fine. Maybe it isn't getting enough air or is overheating or both. I guess it could always be the carb again but the overheating idea just came to me because i had such a nightmare with it last summer and it always seems to break down on the sunny days Any similar experiences you guy could share would be greatly appreciated as it might save me pushing it 4 miles down the motorway/free-way to the next exit in full gear! thanks.



just before i forget so far i've :
checked/cleaned the fuel line - seems clear
checked the oil level - seems fine
added some fuel additive just in case

thanks again
Vii