Motorcycle Repair: Yamah yz125 staling, yamaha yz125, middle groove

Question
Hi, i have a question, maybe you could help me out. I have a Yamaha yz125 1997 motorbike. The problem with it is what if you hold down the gas very fast it starts to twitch and stals down. But if you rev bit by bit, it's ok. but if all the way down it's start like to pump gas but it's not enough and stalls. so you have to accelare by little wrist turns, not max.

my friends tell me it's a problem. maybe you have dealt with it before. hope you understand what is the problem. if you just started moving and would pull the gas all the way, all wrist down, it stars pur-pur-pur and stops. but if you give it little by little, it's ok. is it a problem or is it all 2 cycle motorbikes are likes this?

Sincerely,
Sarunas

Answer
Check the carb the main should be #350 and the pilot jet should be #50. The slide needle should be in the middle groove.Check the float level which should be parallel to the base of the top of the carb set the mixture screw at about 2 turns out from seated. Put in a fresh spark plug and go down one number on the plug this will be a hotter plug.Example if existing plug is a B8ES then go to a B7ES it should help burn the fuel better.