can anybody tell me why my yahama 250 enduro spits and sputters?

Question

i changed the spark plug and even tried a different gas mixture and it still spits and sputters

Answer 1

Always give year, make, engine size and model # when asking questions.
If it's an older model with points - adjust the timing.
Dirty carb
May need piston and rings - check compression
Reed valves may not be sealing - remove the reed block (between carb and cyl) and hold up to the light.
Just some suggestions.

Answer 2

Sounds like a dirty carb. If you have not run this bike every day, that's most likely what it is.

Answer 3

Cause its not an American made motorcycle