husqvarna 455 rancher that run great for about 5-10 min, then boggs down ?

i also have a husky 455 that run great for about 5-10 min, then boggs down to the point where it won't turn the chain. i've checked if the chain was too tight, mixture is fine, oiling for the bar is working great! it seems like it's firing on every other stroke! i shut it off for about 5 min. start it up again, & it runs great for another 5 min then does the same thing over again! i haven't messed w/ any adjustments, and i've checked the fuel for water, fuel lines look good also. filter is nice & clean, could the ignition be heating up? any help would be great.....