Hi newbie to the forum
I have a kit car with a cbr 900 rrv engine in it, it has been running fine for years but after the usual (post winter) rebuild this year its not been right.
I have done a complete rebuild, with ultrasonic clean, and after that it would start and run fine until it gets hot and then its starting missing/bogging and as it gets hotter it starts cutting out at low revs.
When hot it really starts to smell of fuel and when i stop and look in the carbs its clearly over fuelling.
The carbs also make a strange noise (when engine if off) but its not clear if this is still adding fuel to the system or something else see the attached video

I had these carb on and off so many times and stripped,cleaned and rebuilt them and recently got a new set of needles (second set this year) but the problem is still there.
Carbs are running a dyno jet kit

any help appreciated as this has been going on for a few months are its driving me mad and means i can't use the car and just don't trust it.

Thank Pete

 

Wow, that's a lot of fuel. You have an issue with your float level. Not adjusted right, bad float needles or they're getting stuck. The float needles with their rubber tips sit down inside of a brass tube. Have you polished the inside of that tube? I use a split toothpick in a drill on low speed with a piece of scotch bright on it. Then follow up with some Brasso brass polish to make them smooth. If your float's have metal tabs on them, then they're adjustable and need to be checked. Also make sure the floats are not leaking and do in fact float.

 

Thanks for your reply it wasn't a cleanliness issue but your post got me thinking so i sat down and listed the key issues and realised that it was all carbs behaving the same way so it was unlikely a cleaning issue (as im not bad at it) so then i thought what connects all the carbs and i realised that the fuel overflow does and runs back to my tank. The tank has a breather or should have but it was blocked, this caused a vacuum to build and then suck the needle open, the extra fuel would then close the needle again until it leaked out into the inlet and then it would do it again. When i turned the engine off this continued until the tank pressure normalised which took a few minutes.

Just taken it out for a run and all seems good now sp hopefully thats it.

Thanks for the help.

Cheers Pete

 

Sweet, glad to hear that. Sometimes it's just a nudge to get you looking from a different POV. Enjoy the ride.