Hi guys, I have a 1994 cbr400rr nc29 that seems to cut out and seems to missfire at idle especially when warm. I've exhausted most of my options on what to change to attempt to fix it now so I'm after some advice. In my time having the bike I have done:New spark plugsNew ht leads/ plugs Checked coil pack resistances full carb rebuildCarb balance / tune done professionally New thermostat New fuel pump points New fuel cutoff relay New carb bootsCoolant clean New carb trumpets (gf racing) I will attach videos of pre and post carb balance. Any help is much appreciated. I've been trying to fix this bike for over a year now. It's rideable but very annoying with it cutting out at traffic lights. Thanks
https://youtube.com/shorts/rw8tsyDYd0Y?si=hYhICYJnXq0-cJLE
https://youtube.com/shorts/cdFbGueSnag?si=-Dj1eIvvygWES6ps

 

Welcome to the forum, does it start to run rough prior to cutting out? If so would suspect some dirt still in the carbs idle circuits.

 

​​​​​​It does start to idle a bit rough and almost run on 3 cylinders but I've had the carbs ultrasonic cleaned so they should be good surely?

 

Not so sure, these carbs can be really difficult to get clean sometimes requiring 2 or 3 goes due to the hidden passageways.
It certainly sounds like a fuel issue.
There are some very good carb cleaning guides on the forum that highlight the issues that can occur.
Search On IDoDirts posts.