New here at CBRforum. Live in Denver , CO. I purchased a used '98 CBR 600 F3 (15k miles) last year , run great, replaced chain set , rear tail fairings, rear tire, recently hard to start when cold (also previus idle not very stable). Got worse to the point that cannot start anymore if around 40F. Starts good around 55F-60F or higher but I have to give gas , will not fast idle. Choke works( I can see enrichment valves opening), replaced spark plugs, air filter, fuel pump works (full power , running great when hot).
Decided to take the carburators apart and I noticed somebody replaced the jets (slow jets 40 an all, main jets 138 on no.1 & 4 and 140 on no. 2 & 3. The bike does have aftermarket header & mufler (vance & hines). The pilot screws are: no1- 2 1/2 turns out, no2- 2 1/2 turns, no3-1 1/2 turns, no4- 2 turns. I did clean all passages and jets with carb cleaner but they were not visibly dirty , a bit of black on pilot screws. I did noticed the air cut-off valve that is mounted to the side of no 4 carb does not flow any air to the hose (normal?). Any sugestions. I really apreciate.Thank you

 

Welcome aboard Mitricanic.

I suggest asking the guys in the F3 section for similar experiences &/or issues. Hopefully someone will be able to help you asap.

 

Welcome to CBRF!!

 

welcome to CBRF

come and join the F3 group https://cbrforum.com/forum/groups/cbr-f3-group-29/

 

Hi & welcome to CBRF!

 

Hey bro - post on up in the F3 section. You'll get lots of replies there.

Welcome to the forum, lots of knowledgeable people there to help you out.