Every so often, it loses power, backfires & eventually dies. To start it back up, I have to choke it about halfway, and it fires. Then I have to take out a big srewdriver and bang on the carburetor repeatedly, and that seems to fix it, until it does it again! Now I'm no expert on carburetors, but could the needle vavle be improperly seated, or maybe debris in the fuel system?

 

The back fireing can be due to a stuck float in the bottom of the carb(bowl)...
If the carb starts to run low on fuel it will cause a lean condition and possible backfires.
(what color is the plug)....when you tap on it (or bang as you say) You might be freeing up the float enough to allow the carb to fill back up.

I would pull the carb and give a good cleaning and some fresh fuel.


I will say...I have no idea what a "little champ 100" is ?

 

It is a 91 Yamaha Champ YFMB 100.
Great for trail blazing.