Yeah my 2005 650 is being a pest. When I kick it sometimes I get a backfire (Pop) or a mild backfire were it sounds like someone is in the bushes and trying to get my attention (pssst!)
I believe I want to check the valves 65.5 hours (3010 Km's) got the bike around 20 hours never checked the valves (I know I know) but I baby her. Want to also fix the oil weep deal issue and when it goes again, going with Orange Berg kit.
Reading the Doc, I learned that kicking with the electric start was the way to go, because that it was cold and the oil thick the starter was not gonna do it with the 5 amp battery (now Ive got a 7 not installed yet)
One day I swore the started did not disengage and was spinning around with the engine. I was like this is an odd noise coming from the bike. I stopped the bike turned it off, started it again same noise. Did it again same noise. Road it home slowly at roughly 50km/s Only 3 minute ride or less. Let it sit for 5mins started it, no funny noise.