Hello all. New to forums in general so sorry if I'm supposed to introduce myself... I have a 2000 cbr600 f4 fy carb runs well it has a stainless 4 2 1 manifold unknown brand stock one rotted at collector a leovince shortened titanium slip on air filter is a high flow brand is that performance over stock filter? Anyway cleaned carbs properly all airways cleaned ect all stock fueling. Fuel pump started playing up so installed electronic pointless system onto stock pump worked flawlessly
​​​​​​ Now the problem if it is one. As the temperature dropped the bike seems less keen particularly over that magic 7 8 k rpm which id exspect the bike to perform better when cold denser air so I'm questioning maybe it's lean? Also when cruising light load the engine sputters just like a 2 stroke does under light throttle cruising which may be a carb thing but I'm not so sure she pics up fine although did hesitate in second when I gave it the beans. Anyone had any experience with these bikes add there two pence worth? Need a dynojet which is only available as stage 1 for stock setups on there email on my bike Thanks. I'm newbie to larger bikes loving it previous to this I had a 2 stroke suzuki ts125r

 

New guy to CBRs here too but I've had decades working with carbs. I just recently got a 1999 CBR600F4 and used to have a 1992 F2. Cold weather can bring out issues that you will not see in warmer weather but usually only with starting. Once up to operating temperature the system usually works as designed. I have read these bikes are generally rich in the jetting from the factory. It seems like you are having issues at low speed and high rpms. Not that you want to hear it but usually low speed issues are related to something dirty in the carbs or an air leak. Higher RPM problems are usually fuel delivery.

If it was me, I would pull the carbs apart again and clean everything twice. The smallest piece of debris can bring up an issue. Also I would replace the fuel pump completely instead of fixing the current one. One thing I always do is replace the carb boots between the carbs and the head if they are stiff and not flexible. The F2 I had gave me fits getting the carbs balanced. It ended up being the rubber on the carb boots was hard and dry causing and air leak. When I replaced them the new rubber sealed much better. In the cold temps your carbs could be drawing air by the old dry carb boots and once they warm up they seal better. Also I would look at the petcock valve and screen in the tank. On a 25 year old bike that could be a source of restriction at higher rpms if it is partially clogged. Good luck