I need help. I have a 99' cbr f4 and it was running fine till maybe 2 weeks ago.When its cold it runs and idles fine ,but when it warms up the idle starts to jump and down till it shuts-off. It starts back up like nothing ,but when u try to take off it dies again .On the highway and streets it runs fine its just in idle when it acts up. Any idea whats wrong with it .thanks for advice

 

I just got the bike like a month ago. I have done an oil change,adjust chain,brakes,and install another gas tank. Do you think it might be the spark plugs ? i dont know how old are they. Any help thanks

 

YES. God knows how long the PO had those things in there. Also change your air filter.

Since you changed your tank, make sure you didn't bend the petcock, or kink the line that goes from the tank to the pump. Also make sure the vent hoses on the tank are not kinked, either.

 

Thx . I going to put in new plugs and see what it does.I keep u updated

 

AND air filter. That's non-negotiable, you don't know where that thing's been. That bike sucks in a L O T of air. My F3 needs a new filter every 2000 miles.

 

OK, I changed the spark plugs it does the same thing .It has a clean K&N air filter . I was told it might be a sensor or a vaccum line but, I check the hoses and everything seems to be in there place. any ideas ? I think the carbs might need to be adjusted but,I dont know.It werd runs fine cold and warms up and acts up.Its crazy

 

Yep, if you did everything I said, then the next step is to pull the carbs out and give them a good cleaning and inspection.

 

I have the exact same issue.

Starts fine and runs fine while cold. 20-30 minutes later once it's nice and hot, pull up at a traffic light, and the idle will just tend to want to die. Not always, just often. And only when warm/hot. Needs plenty throttle to not die upon 'takeoff'. I've also had it instantly die on throttle in the same situation, but not completely, and just slowly pull itself back up.

I've had the bike ('00 F4) for two years now, and only for the last month or so has it done this. Took it in to the shop. Oil has been changed. Air filter has been changed and is practically brand new. Carbs have been cleaned and synched. Twice. Air/gas mix is fine. Spark plugs were changed, but before it started doing this (only practically 300 miles or so), i think. Normal NGK's, unsure if it's poor quality plugs, incorrect 'distance' on the conductors for the spark, or something entirely different.

I thought it might be carbs, then some sort of anomaly with maybe too much air for gas taken in. I don't know. Ran out of ideas.

Halp?

later edit: unsure if this is related, but thought i'd give any symptom i can. Ever since the year started, i think the battery's been kinda low or something, because if i have the instrument panel lit up, i can see the light intensity go down significantly as i pull the front brake lever and the brake lights go on. Same with cooling fan starting up. The bike is starting and running fine for the first part, on a daily basis, however. So i don't know if battery's an issue. The battery, however, is at least 3 years old.

 

how many miles?anything over 16000 do a valve adjustment if the carb cleaning and sync doesnt work 2000 f4 famous for doin that at 16-18k and above that should fix the problem did to mine after i spent a ton of money i went from carbs, plugs, stator, cdi, to finally valves which fixed it but at which time i was so aggrivated i traded it in for a newer bike so dont do what i did if carb cleaning doent fix it do the valves and spare yourself my frustration.....good luck

 

Valves is what I would suggest. Check them anyways. My '01 f4i was way out of spec at 8k so I wouldnt necessarily rely on the 16k rule.