Its a CS 490 and the saw starts fine, runs strong for a bit, then suddenly bogs down like it's starving for fuel so I decided to dig deeper after I already checked all the usual suspects like carb, fuel filter n all, anyway, in my digging I came across talk of the check valve in the fuel cap being a hidden troublemaker and I just wanna know cos I'm still quite skeptical, could a stuck or faulty valve really be causing this much of a headache?