Hi guys, I'm new here. I picked up a 1994 cbr400rr nc29 last year. Since I bought it I've had an issue where it cuts out at idle quite often and sounds as if it's running on 3 cylinders. I feel I've exhausted my options with what it could be now so I'm after some advice on what to look at next.
In my time trying to fix this I've done:
Full carb rebuild
New spark plugs
New 3d printed stubby carb trumpets (gf racing)
New fuel pump points
New ht leads
New fuel cutoff relay
Carb cleaned and tuned/ balanced professionally
New thermostat/ coolant clean
Checked ignition coil resistances

This video is from before I had the carbs balanced https://youtu.be/rw8tsyDYd0Y?si=aiB5aqe_XqiUxZqO

This video is from after the carb balance. I have not managed to get a video of it cutting out post balance.
https://youtube.com/shorts/cdFbGueSnag? ... btIBCkjnDB


The bike is only ran on shell v-power.
I'm based in Telford If anyone is local and could have a crack at it.
There may be some things I have missed.
Any help would be much appreciated.
Thanks

It still cuts out post carb balance.

R2fst04 wrote: Sat Mar 08, 2025 1:11 pm New 3d printed stubby carb trumpets (gf racing)
New fuel pump points
New fuel cutoff relay

Not quite sure how you came to the conclusion that these would solve the issue

My money is on a carb related issue. Who did the clean and rebuild?

MadMotoUK wrote: Fri Mar 14, 2025 11:50 am

R2fst04 wrote: Sat Mar 08, 2025 1:11 pm New 3d printed stubby carb trumpets (gf racing)
New fuel pump points
New fuel cutoff relay

Not quite sure how you came to the conclusion that these would solve the issue

My money is on a carb related issue. Who did the clean and rebuild?

I sent them to a shop near me to get them ultrasonic cleaned then rebuilt them myself. They had already been rebuilt when I bought the bike but I did it again for peace of mind. New points because if the fuel pump isn't functioning properly the bike won't run properly. New carb trumpets as mine were battered to oblivion. And new cutoff relay as I had read on other bikes the fuel pump can overheat and cause running issues.