2001 ZX6-R Starting Issues

[V1]

Need some help troubleshooting why the bike will not start, and why it runs so poorly when it does. When it does run, it will shut down whenever the RPMs go above 4000, or when heavy throttle is applied. The carbs were removed, disassembled and cleaned. It did not fix the problem.

I want to believe that it's just a fuel delivery problem, but I will need some guidance in the troubleshooting process.

 

[ARCOgraphite]

Did you clean the in tank screen? Make sure the ignition V++ and GND are healthy too.

 

[V1]

No. I'm assuming that involves a complete fuel drain and tank removal. I'll have to check the ignition wires and grounding cable.

 

[JetStar]

When you drain your tank drain it through the petcock with the cap on. Observe the flow. This will verify the petcock screen and the tank vent. Does the bike have an automatic petcock, if yes, that could be the problem. Does it have this problem in the prime position as well?

 

[V1]

I am not aware of any petcock valve on that bike that allows fuel to be drained. The bike belongs to my brother, so that's why I don't know. The only valve on the fuel system that I'm aware of is the OFF-ON-RSV selector.

 

[V1]

Ok. Fuel was bad to begin with, but I also believe that the fuel pump is dead. Bike runs at idle, but as soon as throttle is applied it bogs down and dies. So here is my next question:

Does the fuel pump run to prime the bike? For example, when the start/stop toggle switch is pressed from "stop" to "run" should I hear the little pump make some noise?

If not, how can I test the pump to see if it's working properly?

 

[boraticus]

Not familiar with the bike but I am familiar with vacuum fuel valves. Many, if not most new bikes have a vacuum controlled fuel valve. It has a diaphragm in it that responds to vacuum pulses from the engine. When the engine stops running, the vacuum is released and the diaphragm automatically stops fuel flow. If the diaphragm is weak or damaged, it will not allow passage of sufficient fuel to operate the engine at higher loads. That's the first place I'd look. You will most likely have to drain and remove the tank to service the fuel valve.

I'm not sure if that bike would have or require a fuel pump. Most bikes with fuel tanks mounted with the lowest part of the tank (fuel pick up area) above the engine don't need a fuel pump unless it's fuel injected.

But since your bike has carbs, and if the fuel pick up is above the engine, I doubt that there is a fuel pump involved. Not being familiar with the machine, I most certainly could be wrong.

 

[V1]

There is a fuel pump, and I verified that it is working. I also added fresh gas, but I still have the same problem. So I think we're going to check out the plugs/wires as our next step.

 

[sunruh]

on my cbr600 when the battery was dead(ish) it would stumble and cough and sputter. if you could get it into the upper rpms it would run fine (alternator finally putting out enough juice to all the items) otherwise it was horrid. whack the throttle open and it would die.

food for thought.

 

[V1]

Thanks for the info. The battery is about 2 years old, and still holds a charge. The bike cranks and starts normally, for the most part. It idles fine too. Not rough or misfiring. But the RPM will never exceed 6k. Any more throttle causes it to just choke out. I just don't know if it's too much fuel, or too little, or what the heck.

 

[sunruh]

how long will it idle?

for grins, can you hook jumper cables to it and run it up the rpm range?

fuel or elec. gotta narrow down which.

any clogs in the air intake? like a mouse nest! or wasp nest! or in the exhaust pipe. i've seen both ends plugged by "stuff"
any wires chewed on?

 

[Craig750]

So you need to work out if it is electrical or fuel. That will help.

Have you checked both the fuel pump pressure and flow?

If it is electrical it could be an intermittent problem with a connection, switch, sensor, plugs or the ECU.

Some bike owners have reported faulty sidestand switches causing ignition problems. That is an example of how diverse an issue can be sometimes.

See if you can find someone to swap bits and pieces over with, or a friendly dismantler that may help you out with parts.

 

[V1]

First of all, thanks for the help people. Now here's what I've come up with so far:

The fuel pump does work. I haven't checked flow or pressure, per se, but when I crank the starter, it pumps plenty of fuel out of the hose. A new fuel filter will be added for good measure ($12). The air filter is unrestricted.

Yesterday I pulled the carbs and cleaned them out very well. All four butterfly's were in alignment. Diaphragms and springs were intact. Vacuum lines looked in decent shape. There was some gunk in the float bowls, but nothing jaw-dropping. A few jets were slightly restricted, but still not too bad. One of the main jets had only half of a rubber o-ring on the seat! Can't explain that one... except maybe my brother and his friend lost it last year when THEY "cleaned" the carbs.

Since the bike is pretty easy to work on, I put it all back together just to see how it went. Better, but still not right. The RPMs will go all the way to redline now, but slowly. It idles nicely, and RPM's go right up to 5k, but anything above that requires full throttle.

So that's when I called my brother to get some more information about this problem. He said that last year the bike was running fine, and then one day it just started bogging down out of nowhere.

The bike has coil-on-plug ignition. So I'm starting to think that MAYBE one of the coils went bad. New coils cost $95 each. I'd like to bench test the coils, but I'm not sure what the best way is.

 

[bigbird_1]

If the engine will redline, but slowly, I don't think you have have an ignition problem. Gunk in the float bowls, even a little, can mess up fuel flow through the small bypass or bleeder ports. The missing part of the O-ring bothers me. I would disassemble the carbs, clean them really well by soaking in cleaner, thoroughly dry them with compressed air, get a new kit for each carb, and reinstall. You don't really know what your brother did or didn't do. Start with a fresh known baseline (new carb kits) and go from there.

 

[AuthorEditor]

I bet it's the carbs too. As soon as someone tells me they just cleaned the carbs and they are having problems I suspect the carbs. It is very easy to have the teensiest piece of crud plug one of the jets, or the float might be sticking, or one of the screws is out of adjustment, etc. A lot of times O rings will rot out and then a piece of that rubber will plug up something. Sometimes somebody puts the needle valve for the float back in upside down. The list goes on and on. I'd focus on the carbs. One other thing, make sure there isn't a kink in the fuel line or a restriction at the fuel filter. Maybe remove the fuel filter entirely while you're troubleshooting. Here's a link that talks about adjusting carbs: Carb adjustment

 

[SteveSRT8]

I'm with the carb crowd.

Been going crazy with my MIL's big Yamadog cruiser. Carbs are gunked up from sitting with [censored] 90/10 fuel.

You must be meticulous in the extreme to get those Japanese marvels to work right.

 

[AuthorEditor]

I don't know how many times I've cleaned a carb only to have to do it all over again because something wasn't just right.

 

[V1]

Great! Then I'll refocus my efforts on the carbs before anything else. I like the idea of working from a known baseline. Working from more obvious to less obvious, etc. The carbs will be disassembled, cleaned, new o-rings throughout, and checked over.

But can bad carbs explain why the onset of poor performance was sudden and not gradual? Once again, my bro said that the bike became boggy out of nowhwere.

 

[SteveSRT8]

yep, that was exactly what happened to the Yamaha I mentioned.

Ran sweet and perfect for ages, then suddenly developed bad manners. These carbs are VERY complex, with multiple microscopic passages that require compressed air and a hospital clean assembly.

 

[AuthorEditor]

Quote:
But can bad carbs explain why the onset of poor performance was sudden and not gradual? Once again, my bro said that the bike became boggy out of nowhwere.


Yep! All it takes is a teensy piece of crud to get lodged in one of the jets. I've seen fresh fuel come out of a gas station pump with all sorts of crud in it. On my boat I filter all the fuel before it goes into the tank and the filter funnel catches a lot of crud. It's a good reason to run with a fuel filter on your motorcycle. Sudden bogging can also be caused by a bad load of water-laden gas.