Hi, when I try to rev the bike when it is idling the bike labors and dies. The gas was smelling of varnish so I drained the tank and put new gas in it. All four of the spark plugs were black/burnt so I replaced those too. I have to start the bike with the choke on and i can never get it to run if I take the choke off more then half way. I have let the bike warm up and it sill wont let me rev. Any ideas? I have no idea what I need to do.