I hav ea 2007 250ex it is popping when i let off throttle jetting is fine could it be a vavle

 

It could be a valve, but it sounds more like a lean condition on the pilot side. How do you know the jetting is fine?

 

If it has been running fine all along, then it may be that the pilot (slow/idle) jet has gotten gummed up from nasty modern fuel, etc....leaving you with a lean condition. Or...you may have a leak in the intake (air filter or intake boot), giving you to much air, and again making you lean.

If it started right after you did a rejet, then you are lean somewhere in one of the circuits.

 

mine pops every now and then aswell but only if its idling to high because i need to shift but its in the shop right now my choke didnt work and it stalls in first so i asked them to look at the jetting they did