I have a Californian model fzr600 which I purchased K&N double cone air filters for. The bike obviously needs re jetted or tweaked as a result as it is going like a bucket of s***! Just looking to find out what jet sizes I should get or can i adjust existing carbs in anyway. Any help would be greatly appreciated.

If you have increased the airflow through the venturi then you must increase the fuel as well. It will be running weak so try enrichening it first. If it won't accelerate properly then you will have to rejet and rebalence the carbs. Try one size up from what is already there, should have a number stamped on it. It is best to do any work like this on a dynometer as the fuelling can be fully sorted.

cool. do you mean upscaling the main intake jet? I havnt yet pulled the carbs out to study them, so is there ONE main intake jet or four individual jets, one for each carb that need upscaling? thanks again

cool. do you mean upscaling the main intake jet? I havnt yet pulled the carbs out to study them, so is there ONE main intake jet or four individual jets, one for each carb that need upscaling? thanks again

One for each carb. Go to a specialist.

you junked the oe airbox and fitted individual pod filters?

one size up on the mains is nowhere near enough. you will need to go up maybe something like an increment of 20 - you've made a huge change to the airflow. if you continue to run it without rejetting you will melt valves and possibly pistons.