In a nut shell, have an 2004 CRF 250X. Top end sort of (didn't eat a valve) crapped out. Turns out the cam bearing gave out and lost a shim. Shop that worked on it didn't find any top end damage and replaced cam with a hot cam stage one, something else I can't remember and reshimed as they said the intakes were tight. The bike started perfectly before the work and crap out. Here is the issue, the bike won't start at all without choke and then only when the ambient temp gets above 80 degrees. Even then I have to roll the throttle up a crack to catch. I have been up and down the slow jet sizes as well as the main jet. Once the bike starts, it runs well, although it is way to rich right now. Does this sound like a valve issue or perhaps a carb circuit issue? What other circuit affects starting besides the slow jet? Obviously, it isn't getting enough fuel without choke on and the ambient temp being up, but the fact it runs fine once it does start is a mystery to me. HELP!