Bike shut down between 60-70mph

[Innersole]

I have an 06 gs500f, I'm new to riding and currently have a problem with the bike, recently had a new chain and sprocket, then I had an issue with bike it wouldn't start so I took it to garage and they found water in the tank due to faulty petrol cap so they replaced that and drained all the water from the carbs and tank, I now had an issue yesterday riding 60-70mph the bikes revs went down to nothing then back up to normal then did the same sounded like it was choking then it died on me again but you can feel the power dropping and going up as you hit about 60mph+ I looked through service history and spark plugs haven't been changed in 17000 miles so I'm doing that next week could that be the issue or something else?

Thanks

[Bluesmudge]

Make sure the carb vent hose isn't routed facing forward. At high speed, wind can blow in there and mess everything up. It needs to be routed behind the engine or airbox so wind can't get to it.

[The Buddha]

Also could be a tank that's not venting.

Now, carburetion is related to throttle position. Relate it to throttle position and not speed or rpm. Say it occours @ 60, in 6th, so its 5500 but its also 1/2 throttle. Then if you run it @ 1/2 throttle in 2nd gear, it may occour. That = carbs and most likely with the diaphragm having a little rip.

Easy to diagnose and find and fix.

Cool.
Buddha.

[Innersole]

Cheers guys! I'm going to have a look at what you said this weekend and hopefully fix it