so,

i've got a 1994 CBR600F2, UK model running what i believe to be a VP40A carb (based on google, not had a chance to have a good look at it)
And i've been trying to find out the information on what jets i'd need, and how in the world you replace the jets on a carb and adjust the pilot screws.
its currently running:
-stock airbox with a K&N filter
-200mm low tail shorty exhaust with DB killer (obviously not the one in the pic i posted :P )
-standard carb, no idea what jets are in it currently, could be standard, could have been changed by previous owner.

My reason for wanting to get it sorted is that its got a rough idle, and sometimes feels underpowered at low RPM's, it occasionally bogs on the motorway too, when cruising around 5000-7000rpm (this might be a seperate issue, it only happens for <0.5s or so. but its still noticeable)

basically, what jets do i need, and is there anything i'm missing which could be wrong based on the info i've given above (if you need any more info, let me know!)

Thanks in advance!
-Vaughan

 

Factory jets are fine for your config, still too rich. Your issue is dirty clogged carbs.

Spray carb "cleaners" no longer work due to removal of chlorinated compounds. They need to be completely disassembled down to every last nut, bolt & individual component. Everything scrubbed with brushes in PEA-based fuel-system cleaner, including hidden secret passages in carb-body. Everything ultrasonic soaked and micro soda-blasted. All rubbers replaced: float-valves, float-bowl seals, fuel-rail O-rings, pilot-screw O-rings and even slide-dialhragms if needed. Float-heights set and carbs synced.

All this is lots of work! I suggest sending to pros to do it. Carbs will come back factory-fresh clean and bike will run like brand-new off showroom floor!

https://customcarbservices.com

 

Thanks for the reply man! it's good to see that you come to the same conclusion i did about it!

thanks for the recommendation for customcarbs, sadly i'm based in the UK though so i'll have to find someone a bit more local

i'll be sure to post an update once i've got it sorted so if anyone else has something similar they'll have somewhere to look!

 

I totally respect what Danno says - and he is right - the most sure-fire way to fix this is to rip those carbs down to the components, replace everything with OEM, or a kit like this, and start fresh.

https://www.revzilla.com/motorcycle/...ku_id=10275927

(or you can buy a "Chinese kit" for less than a quarter of the price. )

HOWEVER

My bike gets left to sit a lot, and the idle jets clog up, and then it runs like ****. I just pull the carbs, flip them, swap the idle jets for a $10 ebay set, and it runs like it did in 1996. The blocked jets sit in a glass jar full of carb cleaner until the next time I need to swap them. I don't even poke them clean anymore.

If I am right - your idle jets are Keihin type Pilot Jet N424-21 - they are idle jets, I've had both genuine and aftermarket, made no difference whether I spent $15 per jet or $1.

How much is your time worth? ;-)

 

Chinese kits can work. You can use wire-gauges of different sizes to measure jet sizes. Once you've found wire that fits snuggly into stock jets, use this wire to measure replacement jet to confirm it's same.

Also make sure to poke out all bleed-holes in emulsion-tubes and pilot jets. Dried petrol turns to plastic and you'll find poking holes pushes out little plugs like grains of
sand.



The stumbling ranges you're getting is from slow-speed/partial-throttle circuits. So focus on cleaning parts of carb responsible for that range of operation.