I have a 2004 Eiger 400. This machine has always been reliable and trustworthy. Lately it takes an act of god to start it. Turns over, pops, pops, pops some more and then eventually fires. I have emptied and changed the gas and the plug. Added carb cleaner. Removed, disassembled the carb, blown it out, re-assembled with same problem. When it gets running it runs great. No issues while its running. It may stall once or twice till it warms up. Even after riding it, if you shut it down it starts hard. Any thoughts?? Your help is appreciated.