Hi

I'm new here so firstly hello. I hope there's some hardened cbr carb experts on here.

I have a 97 cbr 600 fv which I bought as an old dog for winter. Long story short its run rich ever since I had it - previous owner had installed dynojet needles but 144 main jets and it was running at 11.5:1 a/f ratio on the dyno full throttle @10500 rpm ie pig rich. Anyway after several rejetsand dyno runs I've come right down to 130 mains which gives 12:5:1 top end so pretty close to my standard tuning target of low 13s.

​​​​​​Anyway...came down another two sizes this week, reinstalled the carbs, took it out for a blast and its now going as rich as 8.8:1 when you give it full throttle! I've had the carbs off again and double checked everything. The mains I've fitted are 126s and the sizes are definitely right, the float heights are all 13.7mm as per the manual, the emulsion tubes are all tight, the needle jets are fine, the slides are all fine, air filter is clean, all air hoses are connected and the air solenoid engages when you turn on the ignition. All I could find was a split hose on the decel tubes which yes could cause issues but surely not at the top end like that. I've replaced the hose but I have questions:

• firstly does anyone know how these decel tubes actually work? They seem to form a bridge between 2 air jets at the intake side. I assumed they were a vacuum operated fuel cut for emissions reasons. Can't figure out how they work though
• Why are the decel tubes only fitted to the outer 2 cylinders
• Could a split tube cause richness like this (I'd expect it to cause lean running as its essentially causing a vacuum leak but how it all interacts with the ram air tubing etc might change things?)

Bear in mind the thing was running ok until this last carb removal so i must have screwed something simple during installation but I just can't work out what

thanks for any input

dan