150cc scooter with fuel issue

[jatgm1]

I have a mc-06 scooter/motorcycle that if you ride for a while shuts off. But if you take the gas cap off, and then start it up it runs again. Like wtf. And when I take off the cap it hisses like there's either negative or positive pressure. I just replaced the gas cap with one from my old gas powered bicycle that happened to fit. I know the tank had to be vented on the gas bike so maybe this will help. Hell if I know.

[jatgm1]

Oh and it has a fuel pump so ya.

[Weldangrind]

That's not the first time I've heard a report like that, although it is the first for a scooter. Perhaps it uses a ball and spring in the cap (like a check valve) and the spring is too strong or the ball is gummed up. Can you do some surgery on it?

[tortoise]

mc-06 scooter/motorcycle (http://www.roketa.com/product/product_detail.jsp?cateID=2610&sonCateID=0&proID=59045) . . that configuration has a pulse pump (http://itistheride.boards.net/post/128119/thread)

[jatgm1]

i replaced the cap with one from a gas powered bicycle, works fine now. i think the chinese forgot to drill a vent hole because other than that their identical..