Ok I bought this bike off craigslist and I got it home, I flushed the tank [there was rust in it] and cleaned the carb [jets were clogged] I got it running and I took it out and when I get to 45mph it starts to choke and die. I thought it was the rev limiter but at lower speeds it limits at 7-8k but in 4th or 5th gear it starts choking at 5-6k.

If I baby the throttle and the stars line up I can get it passed 55 and ONCE I got it to hit 65 going downhill with the wind on my side. What could be wrong?

I was also thinking that the original owner didnt change the oil on schedule, there is only 1700 miles on it and I'm probably going to change it to have peace of mind about when the next change is due, could this have anything to do with it?

I would really like to be able to get on the highway without being a hazard to drivers.

one note is that I can consistently get to 40 in 4th gear by babying the throttle, then when I shift to 5th I gain maybe 5mph then choke out.

what can I do?