loss of power after riding fast for a while

[andyj812]

Hello, I went for a ride on my Will today (Bashan Bs250gy-9) and was after about 20 miles on the highway (actually got up to 60 by gps) I suddenly lost power and couldn't do any more than 51. I reached my destination after another 5 miles. I let the bike sit for a few minutes I got back on the bike to return home. It ran fine for about 5 miles (55+) and then suddenly lost power (max speed 41 gps). I pulled over the side of the road and turned the bike off and opened the gas tank. After closing the gas tank I started the bike and it ran fine the rest of the way home. The last time I went for a long ride I stopped and got gas and was surprised how much better the bike ran afterwords and thought must be better gas. I always run 93 octane and usually has fuel stablilezer if it comes from gas can. I suspect that when I go for long rides the gas tank is not able to vent fast enough and opening the gas tank lets air in. When I open the tank on the side of the road I did not here the shhhhh sound of air rushing in.

Another problem I have is the engines often dies when coming to a stop when clutch pulled in. Sometimes hard to restart. May be that I have the idle set too low if I hold the throttle open a little it usually doesn't die at stop signs. It starts very easily if I turn it of and when cold with out choke if it doesn't die on it own. Where I have the idle set sounds right to me but I don't have a tach to know exactly where its set at