I have a 99 CBR 600 F4. It has 25k on it now. I bought it with the knowledge of this problem. The bike runs fine down the road until it gets warmed up. I will be driving at coast speed of 50 mph in fourth gear at about 4-6k rpms. The bike suddnely starts to cut out. I sounds like it is suddenly runnng out of fuel. If you give it throttle, It bogs more and more and keep losing rpm until it stalls completely. I pull to side of road and choke it full. The bike starts up again and goes down the road like nothing ever happened. 5-10 miles down the road, it will do it again. I pulled off the gas tank, emptied it and pulled off petcock and cleaned it with carb cleaner. I also took off air box and opened up to check air filter. The filter seemed like it was soaked with fuel. Not so bad that it was dripping fuel, but had a strong smell of fuel. There was also fuel residue around where each carb attaches to the air box. The only one that was dry was #4. Are my carb out of synch? Are the valves in carbs sticking? Should I clean the carbs, including jets and all? I am getting a new air filter as soon as possble. I put back together today. I mixed 91 octane, non ethanol gas with seafoam in clean tank and took for ride. Now bike hesitates on acceleration. I didnt ride long enough to see if it would cut out. I was scared to do damage to bike. Can you help me out? Bike had new plugs, in line fuel filter, relay.

 

wow mine does the samething...i was told to..check fuel filter..petcock screen..check for old or kinked lines...and yeah...

 

Yeah, I was also told to pull the carbs off and clean them thoroughly. Then, sync them after cleaning them. I cleaned my tank and the petcock valve and screen in the tank. My bike had fuel pump and filter replaced. I also added about 1/3 bottle of seafoam to 5 gallons of 91 octane, non-ethanol fuel. Now, bike hesitates alot and eventually dies from the hesitation is my guess. I havent cleaned carbs yet. I would suggest doing that, too. I have another thread under CBR F4 if you wanna keep track of this issue and hopefully find a cure!

 

clean and sync carbs, but usually if they were dirty they would do the same thing all the time...Out of sync might be the case though. Theres a solenoid or something that has to do with your ram air system. Make sure this is working properly.

as for eclipser - Sounds like too much seafoam. Carburated bikes dont take much of that potent stuff to get the job done. Ive heard of someone that could only put a few cap fulls of it in before his bike started running like dirt from the seafoam.

 

I'd check the fuel pump before I go tearing the carbs apart (though they could probably use it, anyway). Can you drive it stop-and-go for short distances without issue? Does it only die out at higher RPMs for longer stretches?

 

The bike runs fine when I first start riding it. It has alot of hesitation now since I cleaned out tank and petcock and screen and added the new gas and seafoam. I dont think it is the seafoam since I have never had a problem before with it when putting it into my snowmobile, a Formula III triple with three carbs. I always added alittle when I get it out and ride it first time in the winter. As far a fuel pump goes, the guy before me said that he had replaced the fuel pump and relay. I cant confirm this since he didnt have an reciepts of the work done or parts bought. There was also a new fuel filter. I was thinking that some debris might have gotten into the carbs when I had tank off and air box off. The four outlets that get fastened to eac of the carbs and run into the airbox were sealed with silicone or something similar. I noticed when I had air box off that this silicone is falling off. Can that cause a vacuum leak and cause hesitation? I can ride it just fine( other than hesitation) around my residential neighborhood without it dying. When I get out and hold an rpm for a while like cruise at 50 for a couple minutes. When, I coast then get back into the throttle is when I starts to starve out and die. When I pull to side of road and choke it full, it strarts right back up and is good for another 2-3 miles then repeats itself. I was thinking that maybe my floats were sticking and werent letting more fuel in then come unstuck somehow when I stop. It will only start back up in first also. I can crank on it up to 11-12k with out it cutting out right after. That is another reason I dont think it is fuel pump and or relay or even kinked or restricted line. I wanna ride this bike longer distances but it is a headache the way it is.

 

Sounds like the PO had the same problem you are and couldn't figure it out, either. That silicone shouldn't even be there.

Time to clean the carbs:

https://cbrforum.com/forum/f2-tech-93/carburetor-cleaning-tuning-101-a-96888/

 

I tried syncronizing the carbs yesterday. When I first hooked up my sync tool and started the bike the #4 carb vacuum skyrocket and the others went down. #1 carb vacuum was the lowest and #2 was slightly higher and #3 slightly higher than #2. Could that extreme difference in vacuum between carbs cause the bike to suddenly cut out and act like it is starving for fuel? I didn't get carbs synced yesterday, I didnt have enough time. I will sync them tomorrow and ride it to see what happens. It has stopped hesitating lately, too. There might have been some debris that fell in carbs when I had it apart last. I also found that one of breather hoses from gas tank was restricted. I am replacing it.

 

check main jets in carbs could be clogged also is your battery dieing at all could be a charging issue bad regulator would cause it to start fine but after riding for a while battery will lose charge and will not allow ignition system to function properly

 

Hey, Thanks guys. It was actually the fuel pump relay. It was cutting out intermittently and starving of fuel. I brought to Honda dealership to look at and they figured it out. The guy I bought bike from told me it was replaced so I overlooked it. Thanks again guys.