Hi everyone! I'm new to this, and come in hopes of an answer. I own a '99 CBR F4, and she's been giving me stalling problems for almost two years now. I have had it into three shops now, and spent well over a $1000, and worse than that I'm about to be losing the end of my second season without the bike. Let me jump to the story.

She rides fine when at low RPM's (IE: changing gears no higher than 4 or 5 grand), when I get on it medium to hard she starts to bog out and when I clutch it to rev her and regain throttle response, she dies completely. When I finally pull over to the side and try to start her, I get nothing. It either takes a few min's (about 3-5) of sitting there, or sometimes if I choke her she'll start right back up. (It almost seems as if there is a lack of fuel so when I ride hard she can't get enough gas, and therefore stalls, and when I'm riding 'delicately' she'll drive for blocks. Very weird. My last venture to a shop had the carb's tuned on a dyno, fuel pump was changed (a second time), and she was jetted. Also other small diagnostics were performed. It also seems as if sometimes when downshifting up to a light she'll die out. The last shop I had it at was very reputable, so I have no doubt in their work. I'll probably be bringing it back to them over the weekend unless I can find an answer here. Last night I took her for a spin and we noticed the oil was very very low. We figured this may have had something to do with it such as a low oil cut-off. We added some oil to get me home, and still she stalled and stalled and stalled. I'm sure you can understand how frustrating this is, and I am at wit's end. The first shop had it over a year before deciding to refund me my money and give me my bike back, and now I fear this shop will do the same. I have a crappy after-market M4 exhaust which they claim isn't causing it, and other than that everything is relatively new as far as I know (spark plugs, fuel filter, fuel pump). My next step might be to swap out the exhaust if I can find a used stock one just to make sure that's not the issue.

I really really appreciate anyone's help, knowledge, etc on this matter as I pulled all of my hair out already! Any further questions that you have you may contact me vinnypope@nextel.blackberry.net Thanks Everyone, glad to be part of this forum!

 

It seems like the symptoms you are having would show up in a dynojet run, and with the severity you are describing it should be pretty apparent in the dyno chart. Anyhow, how long after you got the bike did this start happening? What mod's does the bike have?

 

Well supposedly they supercharge Hyabusa's so they have a custom 700HP dyno (www.fastcycles.com). But after everything they did it still stalled. There is no mod's except crappy exhaust and the jet kit. I had a complete tune-up plugs, etc, and about a month after that it started happening. I've had the bike for about three years, but this has been happening since last June or so. The tune-up was performed in May of '04. Maybe they keep missing it since it is intermittent, however I'm sure the thing is probably stalling on the dyno as well!

I appreciate your response as well as any further ideas!

 

I'd also like to add that when I do stall and it doesn't start on the side of the road, sometimes activating the choke will make it start right up.

Does this sound like an ignition problem to anyone? Stator Box?

 

If you go back to the stock pipe you will probably have to re-jet it again. If you go this route, make sure you have them do before and after dyno runs and compare the charts. This is the most objective way for you to check their work and your bikes performance. I've even had them show me charts from stock bikes and bikes with similar mod's just to get a point of reference for interpreting the results.

Besides that, I think it is still your jetting. Perhaps the needle positioning or main jet size because it sounds like you have this problem when you whack the throttle open. Try running you bike at different RPM's and see if you can determine where exactly the the problem is occurring. You might want to look into spark plug reading, as this can give you some good insight into how your bike is running, and can give you clues about the adjustments you need to make. Next time your bike stalls, pull the plugs and examine them.

It's kind of a pain to go through all of this, and in the past I have just gone back to stock jetting or re-jet according to manufacturers recommendation and then tweak from there. If your jetting is far enough out of whack it can take forever getting your bike back to a rideable state using this trial and error method.

 

Right on. Before there was dynos, they pulled spark plugs. When you do, I'll bet she's running lean, especially when "sometimes activating the choke will make it start right up". Activating the choke usually bypasses the idle circuit and main circuit. I would check the movement of the each carb's slide piston. I bet one or several are sticking. If they stick open or closed, the bike will run like yours. I've never seen the carbs on an F4, but can you see the slides when the filter or airbox is off? Move each slide with your finger. It should have some resistance and close smoothly. Does it?

 

Thank you both very much! I'll check into your ideas and get back to this forum. This may take a week or two, so for now, keep the ides and suggestions coming! I do appreciate it very much!

 

Are the symptoms completely intermittent or does it constantly bog at high rpms every time. I've seen similar issues with electrical problems.. the vibration at higher rpms was causing a stalling due to a faulty relay. There are lots of things that can cause a bike to stall or completely die. And if you had it at a reputable tuning shop, i would think they would be able to tell if a bike was running lean or rich and rectify the situation.

 

Yeah i dont know if anyone can help me but i have a 98 F3 and ive only had it for a few months and its ran perfect but i was riding it the other day and it started sputtering like it was out of gas so i switched to reserve it just sputterd to a stop and the battery was dead i had my friend come and he hooked jumper cables to it and it fired right up but i went and got a new battery and charged it up but after 2 or 3 miles it did the exact same thing i know its electrical but what could it be

 

Sounds like your battery issues arent with the battery but the charging system....could be a component or could be wiring. Get a manual (or download a pdf one, search the forum youll find links to one) and follow the diagnostic and troubleshooting steps listed to figure out exactly where your problem lies.