Is this lean or rich? Pops and crackles a little when I back off and it also pops flames every now and then so I've assumed running rich. Goes incredibly well! It's a 09 yz250f and it was only idling for a minute or two at the most when I pulled up. Haven't touched anything on the bike since I got it about a year ago and I've put about 15-20 hours on it. Should I be concerned??