I have a 2009 CRF450 that started having a running issue halfway through my ride the other day. The bike runs amazing on the gas, as soon as I let off it completely goes dead. I suspected a fuel pump, put in a new one and I have the same issue. The bike runs great at all other rpm and will idle if I slowly back off the throttle. I have no clue where to start! Valves are in spec, compression is good, everything has been great until this issue.