Have had my cbr 125 couple of years now n never really had any trouble till
couple of nights ago as I was trying to go to work it would start n tick over on very low revs couple of seconds then cut out left it at home n charged the battery as starting it over n over had taken a lot of the juice up , tried it again today and fires straight up n ticks over merrily but if I apply revs it cuts out at anything over 5000 if I release throttle quick enough it doesn't cut out n goes back to ticking over . Tried riding it along street and it will trundle along at 3000 revs anything over this n tries cutting out . Any ideas ?? Thanks in advance

 

Did this issue come up suddenly, or gradually ? When was the last time you rode it with no problems ?

 

is the cbr125 fuel injected? did you drop the bike recently?

the fact that your bike still starts means that you have gas, air, and spark. however, they are not mixing properly. so you need to figure out with one(s) is the troublemaker.

1) i would check if the air sensor (in some bikes it's called IAT) and all the vacuum hoses are connected properly.

2) Make sure the connection to the battery is tight... loose terminals can cause this. check the charging system, using a multimeter. you can read about this from a recent discussion: https://cbrforum.com/forum/f4i-main-...z-help-144529/ . Also you will want to pull the spark plug(s) to make sure it's not dirty.

3) pull the gas from the tank and check for contamination.