so fuel pump even if the bike is fine at speed and up/downshifting? carbs seem to be getting gas while riding and there is no loss of power and no backfiring. it just happens at idle. seems like it might be hard to test because itll only stall sometimes after its warm at a longer stop after riding a couple miles.

 

Yes...mine at speed was perfectly fine, once I get to a stop it would stall, unless I reved it. It would only happen when hot. Ive adjusted valves, cleaned carbs, tested the electrical system, only to have the pump playing with me as I tuned carbs. Fixed pump contacts, the problem went away! It can idle fine forever, even the fan comes on which would never happen bepfore, it would stall before that.

I remember that it would make it stall sooner if I turned the lights on.

If I were you, I would run the bike without the pump in order to diagnose it, cheap and takes 10 minutes.

I allways tought that a failing pump would be most likely to fail at great speed, but also makes sense that a failing contact cant get enough voltage to change state at idle...
Good luck!!

 

man. ok i really appreciate your help. hah yeah i was just hoping it wasnt the pump cause i know the whole thing is $100+. hopefully its the contacts or nothing too incredibly serious.

 

I would rather run without a pump that have to buy a whole pump...
Theres a forum member that runs the bike without pump with no issues...I've got a friend pro stunter that does the same in all his F4's, says that the only issue is to keep the tank from getting too empty.
Theres also a FACET pump, that people have been using on Africa Twins, that use the same OEM pump as the CBR, and they are cheaper and solidstate, meaning that there are no contacts to burn. There is always a risk playing with a non-oem pump, but these are you options, if the problem is in your pump.

For reference: https://cbrforum.com/forum/cbr-600f4...-137637/page2/

GL!

 

i didnt get around to pulling my bike apart this weekend but had some other ideas as to the problem here. took it out for another ride. came to the conclusion it ONLY stalls when the fan kicks when the bike starts to overheat from idle while stopped. as soon as the fan kicks on, dash lights dim and rpm's start goin to **** and stalls. first of all im switching my coolant to engine ice which says it lowers engine temp by 50deg. also gonna charge the battery on my tender. The fuel pump contacts might be burnt out but i also think my R/R might be starting to go. also might look into replacing fan. probly will change plugs and air filter as well while im at it.

 

this probably the wrong thing to do but it was quick. i pulled the fan fuse so it wouldnt turn on. i let the bike warm up and it never stalled at idle but the bike was getting too hot. this probably be good sitting at a long light or something like that. not sure if this helps diagnose the problem...

 

wouldn't be good*

 

Even for a diagnostic that's too risky, one might end up with a blown head gasket and that's a ****ty isue to deal with. But nice idea though!

Anyway, when your fan turns on, it will create a load on you electrical system, and at idle, your bike might not be producing enough power to keep functioning. It might be due to a lot of things, excess current draw from fuel pump, fan, bad R/R, etc..

You see, the system has a kind of a positive feedback, you have a low producing voltage (running at low rpm) it might not be sufficient to maintain that voltage to power all the devices (too much load), which in turn reduces the available voltage which in turn will affect fuel pump, spark plugs making the bike idle worse (lower rpm) thus producing less voltage, and idle even worse until it stalls.

So, what you might get from this, is that there can be a lot of causes for you stall issues, fuel pump, ignition coils, generator, battery, R/R, kill switch, defective fan, etc!

when I had this issue in my F4, as soon as I turned the light on, the idle got messy, and if the bike was already warmed it would stall completely at idle. Keep in mind that the load from the lights, is less that the load created by the fan. If it stalled with the lights, it would certainly stall with the fan on, even though that the bike wasn't capable of idling properly until the fan turns on.
And in my case, it really was the fuel pump, and it was the first thing that I shoot at, as it was the best known suspect.

Even if the fan thing might seem completely unrelated with the fuel pump, it's related to the whole electrical system which the fuel system relies on.

After charging battery, getting the bike warm and stalling, I would check voltages at idle, 3Krpm, and 5Krpm then post them here, and check the current consumption on the fan. To do that (as I did at the time) just attach you multimeter, in the "Amps" setting and in the >=10A probe, from the fan switch (+probe) connector to the ground ( -probe, you have a ground in the radiator) and check the current. be sure it's in DC current. I can't remember if it was a 3.xx or 6.xx Amp current consumtion in mine. The manual might have that values, but I can check it latter if you want.

With that you can rule out the R/R, Fan and battery for now, without wasting money, except from multimeter batteries.

To bypass the fuel pump you don't have to tear the whole bike. Just some fairings, lift the tank and theres is a fuel filter. Disconnect the tube (at the filter) that goes from that filter to the pump, and connect at the filter the tube that goes from the pump to the carbs. Disconnect the electrical plug from the pump, check the fuel passages for pinches, and turn the tank petcock on.

Start the bike and let it run until the fan kicks in, lights on and (hopefully) smile! ;-)

The fuel pump is not the "mother of all" stalling culprit, but it was the one in my experience.

GL!

 

Nice diagnostic tree there piresito. well written and explained. The only other thing that you mentioned among possible culprits (and one that I've seen in a couple threads as the culprit) was the kill switch. I don't know if there is an easy was to bypass it to check it, but I suppose you could check for a voltage drop acrossed it.

 

Thanks!

+1!
BTW, excessive voltage drop may be caused my too much resistance in the switch/circuit and/or too much current draw from its load.