I have a 1997 CBR F3 that just runs terrible. I'll try to keep this brief, but at the same time I want to give as much info as I can. I have had this bike for 4 years and thought it was strange I had to put a brand new set of plugs in every year. As late fall crept in the bike would run worse and worse, but that next spring with new plugs she ran like a dream. Apparently one set of plugs on these bikes a year isn't unheard of? This winter I did a ton of work to it (new tires, air filter, fuel filter, lubed all cables, brake pads...didn't clean any carbs or anything) and after less than 100 miles of riding the plugs are fouled! I do ride my bike less and less now a days. I ride it to work during the week in stop and go traffic, but do take it out on faster roads at least once a week for a good ride. I'm not sure what other info to tell...I did have the carbs cleaned and put in sync two seasons ago. (done at a dealer) Valves done last year at a dealer. I'm sure if I spent another $40 on plugs it would run great...but for how long? I really hate to be investigating carb issues, but is that the way I should be looking? Any help would be greatly appreciated. I think I said everything, but if anyone needs any more information ask away...thanks in advance.

Oh... one more thought...there is a after-market exhaust on it which was there when I bought the bike, but I'm not sure if the bike was ever rejetted for that pipe.

 

Sounds like somehow its not completly burning all the fuel and is depositing residue behind...
What kind of gas do you use? What kind of oil?
Does it smoke at all? miss fire?

 

Know this is late (just saw the post). Instead of replacing the plugs just clean them and try it out. What struck me most in your post was the after market exhaust -- is it a slip-on or full exhaust? I'd bet it WAS rejetted for the exhaust -- but was jetted tooooo rich. If you pull the carb bank (as a unit) it's easy to tell if it's been jetted -- the needle will have 4-6 slots at the top for adjustment. If you don't have access (or wanna pay $250) for a dyno tune just take the clip and move it up 1 setting on each carb. This will lower the needle and run a smidge leaner. If you're going most of the season before getting carbon on the plugs then you're not off by lot -- I wouldn't change jets unless the needle doesn't help.

 

maybe they keep fouling because your riding with the choke on. yesterday i started my bike and i need to use the choke and i revved it. my friend said that if you have the choke on and ride or rev it it fouls the plugs.

 

Sorry I 'm late to reply to posts you people have generously taken the time to write up for me. To answer some questions above...I run 93 octane, I use the hondaline oil (whatever weight the manual calls for) and it did not smoke or miss fire. I definitely do not ride with the choke on, but I actually thought the cable might be stuck slightly open. It was not. Running out of ideas, I had a local shop clean and sync the carbs. They said there was crud in all four carbs. After getting the bike back it was better, but I'm still not pleased. Although the bike has not fouled plugs (original problem) in the recent weeks, I'm still not satisfied. If I'm in 4th gear @ 4K RPM @ 45 mph the bike runs rough. Not sure how else to describe it. It just feels flat. If I get the rpm's or the mph's up..it runs fine. Same thing happens in 3rd @ 4K rpm @ 35 mph. Runs rough, pick up the speed and rpm's..it runs great. I still think it is a carb issue. Maybe I was just expecting too much when it came back from the mechanic. I read at this site in another post that this bike shouldn't even be run at anything under 6K rpm? Any truth to this? I've had the bike for 4 years and never had to run it above 6K for it to perform to my satisfaction.

Hey chainstretcher....from what I've told you above, do you still think I should do as you suggested. A few other tid-bits I learned from having my bike worked on recently is that I do not have a jet kit in there. Also, I do have a slip-on and not a full exhaust.

Thanks again everyone for replying and sorry I wasn't quick to return.