Help with 81 Gs450L

[Zamtech]

Okay im new to this forum (which has been a life saver for some situations) and am sorry if im posting to the wrong thread but i have reached my wits end. I had gotten my bike running finally after two weeks of working on it, replacing battery and testing the electrical, cleaning the carbs to the best of my ability. I had my bike running for two days, however the bike was running rough with the throttle all the way it was barley moving. Today i wet to start it to figure the problem out and flames came out of my carb between the air box burning my air filter. Need help anything at all would help to get me started.

I am new to this and this is my first bike, so if you could be clear when you explain something i would really appreciate it, thank you.

[Gorminrider]

here's an easy link..it's about cars, but the general idea of it applies to bikes.

http://www.ehow.com/info_12206850_car-backfire-through-carburetor.html

Check the obvious ,easiest first.
the spark plugs ...for an indication of rich or lean running.
Don't expect the most complicated problem until you have checked the easiest things first.Does the bike stink of gas? is the fuel tap vacuum line dumping gas into the intake manifold?are the floats too high?
Lean plugs...an airleak at manifold gaskets,etc etc.
then there's the valves to check, the timing, the sparkplugs themselves
When you think you have an idea what it could be, goto this incredible site and find it,read it.
BikeCliff's Website

[Zamtech]

Thanks for the advice, spark plugs where just replaced although one of them show signs of the engine running rich. Also when i went to remove the carb to inspect it i found that the carb boot had a tear allowing air to go into one of the carbs(not the one running rich of course) could this be the reason why the bike is backfiring to the extent of lighting my air filter on fire.