Hey everyone. Been lurking here for years, but only just making an account because I'm totally stumped.

I have a 2000 CBR F4 with a bit of an issue. The bike runs great until it's heated up, and will randomly die once I'm rolling to a stop. I thought I fixed the issue (details on my "repairs" later) until today on the freeway. 70mph in 6th gear and I noticed the bike stopped accelerating, was frozen at 5500 rpm even after a downshift. It felt like maybe it cut down from all 4 cylinders and the sound went from that high pitched scream to a low gurgling rumble. By the time I slowed down to pull into a gas station the bike had died. Once I let it cool off it started right back up and gave me no problems on the way home, and I even rode it around close to the house for about 45 mins with no issues.

In an attempt at fixing the problem I replaced the fuel filter, and totally rebuilt the carbs. By rebuild I mean ripped them apart replaced all of the gaskets/o rings & installed a brand new jet kit, cleaning everything during the process. The bike ran so good after the rebuild I was certain that the problem was fixed, until today.

Any ideas guys?

Side note: my manual shows that the bike has a fuel pump, but it definitely doesn't have one installed. It's gravity fed from the tank straight to the carbs, separated only by the filter. When the bike died today the gas light came on as I pulled into the station. Is it possible that with less fuel there wasn't enough pressure to gravity feed the engine? And could lack of fuel cause the bike to drop down to two cylinders, if that is indeed what happened?

Thanks for any help.

 

Are you sure that the fuel tap on the tank isn't on reserve instead of 'normal', as this would empty the tank and leave no reserve. Normally as you know, the bike would cut out and turning the tap to the 'reserve' position would get you going again. I had a similar problem on a BMW where the main supply pipe to the fuel tap had fell off inside the tank, so I was running out completely of fuel with no reserve. I think the taps work in a similar way, but you'd have to take it out to check.

 

I wish it was that simple, lol. Reserve is absolutely not turned on.

 

there is no reserve on an f4. You could check the r/r, they are prone to dying especially when they get hot, but Im still learning about this bike.

 

Oh Sweet Jesus....where to start...

I COULD chronicle every issue I have had with heat-related problems on MY F4, but lets start with your specific woes...

First of all, gravity feed alone may be not be getting a steady supply of fuel to the carbs under all conditions. If there is, in fact, no fuel pump...i would question why. You could be spot-on with your comments about the tank being low and starving the carbs. As a reference, the fuel pump should have one hose in, and one out, and it is held in place with a rubber "boot" hanger about 6 inches above and forward of the right-side foot peg, nestled inside the frame (see picture with big red arrow).

If you don't have a fuel pump there, please get one
Bikebandit.com lists one under part#590993, with a price of $112.97.

Next!!!

Ok, fuel pump possibilities aside, you could have an issue with your R/R (regulator / rectifier) as Cjardine stated. The stock ones on F4's are junk junkity junk. I retro-fitted a factory "solid-state" type R/R on my F4 that came from a 2006 CBR600RR. They can be found on Ebay all day long, but you will have to rewire it manually into the F4 harness (connectors not the same). Stock F4 R/R's are what is known as the old-fashioned "shunt" type, and crap out all the time after age. As far as narrowing it down to confirm if that is the problem...unfortunately, no easy way to do so besides replacing it I'm afraid.

Next!!!!

If you have a certain F4 model sometimes referred to as the "canadian model", there is a carb warming circuit tied into the water pump for colder weather operation. You would see a 1/2-5/8 diameter heater hose pointing upward from the water pump on the left side of the bike. This goes into carb #4 and loops to the float bowls on the other 3 carbs, then circulates back into the system via the thermostat housing. Problem is, during hot weather when bike gets up to temp, the coolant is sometimes above the boiling point of gas by the time it is at the float bowls. What happens is the gas inside the float bowls will actually vaporize, and starve the engine of liquid go-juice!

On my bike, I blocked the hoses to the float bowls at the same time I replaced the thermostat (which may also be related to your problem, BTW). Your exact bike might not have this carb heater circuit, but if it does, I would block it off either way - it is not needed in temperate climates, and would at least eliminate one thing on the list.

Any questions on the mess above, let me know. I have resolved many headaches on my bike, but cannot remember every detail off the top of my head - a few prompts to jog the noggin may be needed!