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Discussion Starter · #1 ·
Hi there, my first posting here.
My girlfriends 2008 ZX250 Ninja with 7500mls on it will not rev past 8000rpms when it's under load(it will rev past 8000rpms in the garage while in neutral- but not while riding).

It was going fine but then one day she went for a ride and it wouldn't rev past 8000rpms.

The week before we had been out riding and it was fine(up to and slightly past 95mph) and accelerating without hesitation, then the next ride, the above symptoms.

We've cleaned the air filter, changed the plugs, had the tank off, removed and cleaned the carbs and done a carb synch, taken off the fuel cock and removed the fuel filter. Took the muffler off and ran it without that for a few miles(thought there maybe some in the muffler blocking the gas flow).
We've enven taken off the California emmisions stuff, all to no aval... the bike will still not rev past 8000rpms!!! Frustrated now!

I'm thinking the next step could be to check the timing, but as I say it runs well under 8000rpms.

Any help/advice/if this has happened to anyone before would be great.
Thanks
Kiwi
 

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Sounds like you've done quite a bit of troubleshooting already.

Did you put in fresh fuel when you removed the tank?

Depending on where you are, how much the temps fluctuate, how full you keep the tank, if you use gas with Ethanol, and how old the gas is, the fuel can easily have significant amounts of moisture in it that will create all sorts of odd running problems.

Before moving on, drain the tank and refill with fresh Ethanol-free gas (if available) and 1oz per gal of a fuel system cleaner like Techron Concentrate or Seafoam.


Jay
 

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Discussion Starter · #4 ·
Yes, put fresh fuel after the draining of the tank but not sure whether it was ethanol free or not(will try that tonight). Will buy some Seafoam as well and try that(where do you buy it from- sorry).
We live in Phoenix, Arizona so it's typically pretty warm, but right now the temp is only 70-80 so not overly hot. The bike runs this way with a full, or half tank so I don't think the fuel level has much to do with it to be honest. I thought it may have been the fuel pump but have come to understand it's a vacum system(no fuel pump) so this thought has been discounted now.
Thanks for your help thus far.

Kiwi

Sounds like you've done quite a bit of troubleshooting already.

Did you put in fresh fuel when you removed the tank?

Depending on where you are, how much the temps fluctuate, how full you keep the tank, if you use gas with Ethanol, and how old the gas is, the fuel can easily have significant amounts of moisture in it that will create all sorts of odd running problems.

Before moving on, drain the tank and refill with fresh Ethanol-free gas (if available) and 1oz per gal of a fuel system cleaner like Techron Concentrate or Seafoam.


Jay
 

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Discussion Starter · #5 ·
Hi there Blue Ghost. No mods to the bike, standard carb settings, standard pipe, standard air filter etc. Used to run fine, just one day it wouldn't rev past 8000rpm.... bloody annoying.

Thanks for your responses so far, I appreciate it.

I've also read that fuel lines could be crimped so may try and order some of those as well to discount this as well.
Cheers
kiwi

Any mods to the bike? What were your adjustments to your carbs?
 

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By fuel level I meant sitting with a low level in the tank, which can cause condensation problems.

Any chance there could be a vacuum leak or poor vacuum getting to the fuel petcock? Did it sit for any amount of time? Does it sputter when it stops revving? Will it run differently if you back off on the throttle slightly at that point?
 

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Discussion Starter · #8 ·
No it doesn't make a noise from the gas cap(I know what you mean as my ZX10r race bike whistles all the time from the gas cap). If it's not whistling from the ffuel cap do you recommend changing some/all of the fuel hoses?
What's the snorkel? I've not heard of this before.

Cheers

Is your gas cap venting well (does it make noise regularly) and have you tried removing the snorkel?
 

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Discussion Starter · #9 ·
We generally always leave the bike with a full or over half a tank of gas everytime(never run it real low).

We bought the bike like 4 months ago and have ridden it every week or two since buying it. It does splutter when it hits 8000revs so you let the throttle off a bit and then it will rev again, but then you hit 8000rpm again and it won't go past this.
It revs up to 8000rpm just fine, only when it hits there it won't go any further, then you have to back off the throttle again slightly and hold it under 8000rpm for it not to miss/splutter.

Thx

By fuel level I meant sitting with a low level in the tank, which can cause condensation problems.

Any chance there could be a vacuum leak or poor vacuum getting to the fuel petcock? Did it sit for any amount of time? Does it sputter when it stops revving? Will it run differently if you back off on the throttle slightly at that point?
 

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No it doesn't make a noise from the gas cap(I know what you mean as my ZX10r race bike whistles all the time from the gas cap). If it's not whistling from the ffuel cap do you recommend changing some/all of the fuel hoses?
What's the snorkel? I've not heard of this before.

Cheers
If the gas cap does not vent often, especially when it is hot, it can cause fuel flow issues. High Speed Shutdown

The snorkel is the removable portion of the airbox that restricts airflow. Removing it can smooth out the throttle response to the bike.
DIY- Removing the Snorkel : KawiForums.com Kawasaki Forums: Kawasaki motorcycle forums
 

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TEST FOR COMPRESSION. IF your having issues in compression its most likely a broken cylinder head.

Its important to put oil on the camhead when testing to get a perfect seal otherwise you might have a leak again from the camshaft heads, they have metal rings that go back too but when i got my ninja engine the guy had driven through that and destroyed the cam heads. <---MOST LIKELY PROBLEM

Its not pretty but your going to have to remove the head of the engine and test the cams and valves at top dead center. This means removing the engine and getting it up on a table, twisting the crankshaft bolt until the cams are releasing the valves. checking the clearances will allow you to determine further if its a problem in the lower or upper engine.
 

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At this point I'm still thinking it's something simple that won't require teardown.

What do the plugs look like - dark, light? Will it accelerate cleanly at lower RPMs (4000) and wide-open-throttle (WOT)? Does it get worse as the engines gets warmer or has run a while? Add some choke (1/4 to 1/2) when warm and see what it does - better/worse?

You can find Seafoam and Techron at most auto supply stores and even some Walmarts.

I'm still thinking something carb/fuel related...

Check all the wire connections around the coils and plugs to make sure they are firmly seated also.




Jay
 

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Discussion Starter · #13 ·
The plugs look great, nice amber color(not black or gummed up). It will accelerate away form the liughts nicely, no spluttering/stalling etc.
It isa the same all the time and I haven't tried adding chock while hitting thr 8000rpm's as yet, maybe I nmeed to try that.

I'm hoping it's just fuel/carb/tube related..
Thanks

At this point I'm still thinking it's something simple that won't require teardown.

What do the plugs look like - dark, light? Will it accelerate cleanly at lower RPMs (4000) and wide-open-throttle (WOT)? Does it get worse as the engines gets warmer or has run a while? Add some choke (1/4 to 1/2) when warm and see what it does - better/worse?

You can find Seafoam and Techron at most auto supply stores and even some Walmarts.

I'm still thinking something carb/fuel related...

Check all the wire connections around the coils and plugs to make sure they are firmly seated also.




Jay
 

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Is there some way that the throttle cable has become stuck or caught on something that is not noticable while in the shed and just revving. Perhaps the weight of a rider is binding up the cable in some fashion?
I really have nothing else to offer, but has the cable been looked at?
 

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Good stuff so far, and welcome Kiwi!

Any chances for photos of the bike? How 'bout a video showing the problem during a ride?

Now, things to check:
1.) Have the carbs EVER been off the bike? I read you have stock everything, BUT, while trouble shooting, you didn't happen to bump the carbs out of the intake tubes, no? This sounds like a pinched/holed vacuum slide seal, or a poor fit on the intake boots...
2.) Have you checked the airbox and snorkel for any leaves/ possible blockages?
3.) Tubes, fuel and vacuum - take all of them off, mark where they go, and blow them out, with compressed air, with your lungs, whatever. Make sure they're clean...
4.) If you can't make a video of the bike, please describe the sound with particular references to RPM points...
5.) Have you done a compression test yet?
6.) Are you loosing any fluids anywhere? Oil, coolant?
7.) Concerning the removal of the CA emissions BS... You did this AFTER the problem started? Did you make sure to cap off all the holes where it used to be plugged in? It didn't change the behavior of the bike at all?
8.) Do you know the difference between a bike's sound running lean/rich? If so, does it sound like it's starving for air or for gas? Any pops or reports from the exhaust?
 

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Discussion Starter · #16 ·
Thanks for the words of advice.

My MMI certified mechanic and I are going to take the bike apart tomorrow night and try to sort the issue out. I'll report back after this.
Anyway to answer your questions below here goes:

1- Yes we took the carbs off before and put them back on... the same problem existed before we tookl them off, the same issue now as before(won't rev past 8000rpm
2- Checked the airbox, found a piece of paper and some candy my gf had stashed in the under seat area... cleaned it out, same problem exists
3- Took all tubes/hoses off last time and blew them out with the lungs(no blockages from what we could tell, same problem exisits
4- Will try and get a video over the weekend.. if we don't get it fixed tomorrow night
5- Compression test was fine(can't remember numbers but 1 cylinder was donw a little more than ther other, but not by much
6- Loosing no fluids, no coolant etc
7- Not sure about plugging the holes where we tool tubes off, will check tomorrow night
8- I don't know the difference in sound lean vs rish, but I'm sure my buddy will tomorrow night. Also, no it doesn't smoke or makes any poping noises, just missing once it hits 8000rpms.
Will report back once we get it worked on tomorrow night

Thanks
Good stuff so far, and welcome Kiwi!

Any chances for photos of the bike? How 'bout a video showing the problem during a ride?

Now, things to check:
1.) Have the carbs EVER been off the bike? I read you have stock everything, BUT, while trouble shooting, you didn't happen to bump the carbs out of the intake tubes, no? This sounds like a pinched/holed vacuum slide seal, or a poor fit on the intake boots...
2.) Have you checked the airbox and snorkel for any leaves/ possible blockages?
3.) Tubes, fuel and vacuum - take all of them off, mark where they go, and blow them out, with compressed air, with your lungs, whatever. Make sure they're clean...
4.) If you can't make a video of the bike, please describe the sound with particular references to RPM points...
5.) Have you done a compression test yet?
6.) Are you loosing any fluids anywhere? Oil, coolant?
7.) Concerning the removal of the CA emissions BS... You did this AFTER the problem started? Did you make sure to cap off all the holes where it used to be plugged in? It didn't change the behavior of the bike at all?
8.) Do you know the difference between a bike's sound running lean/rich? If so, does it sound like it's starving for air or for gas? Any pops or reports from the exhaust?
 

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Did you inspect the inside of the float bowls when you had the carbs off?

It's possible there could be some sediment in them that has partially blocked the main jet. If you have them off again, pull the main jet and carefully run a wire through it while spinning it on the wire and spraying it with carb cleaner.

That, or there may be an issue with the ignition (wires/cables most likely).

As spooph noted - did removing the emissions stuff change anything? Is it possible there is a vacuum leak because the system was removed?

Let us know what you find out.


Jay
 

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Discussion Starter · #19 ·
Hi guys,
well we spent a good part of 4 hours last night and here's what we did, all to no luck:

Removed tank
Removed air filter again
Removed top of carbs and pulled out the needles
Drove down to the hardware shop and bought a small washer for each carb/needle
Checked the diaphram for cut's/rip's(all in good condition)
Put the carbs back together again
Replaced(with new tubing) the vacum/carb tubes(after pulling all of them off and blowing through them all- they were fine- no cuts or tears in them)
Above the cam cover there is what looks like a reed valve/fuel filter item- removed this and cleaned it out, then put it back on again
Replaced the tank and air filter- went for a ride.... and the same issues still exists, however it did rev to about 9000rpm this time, however I think this may now be because we fitted the washers on the needles.

We were so frustrated, so then we put a voltage meter on the battery and found the following:

- At idle it's producing about 12.5volts
- At 3000rpms it's producing about 14 volts
- At 10000rpms(under no load) it's producing about 14.5 volts.

Maybe the reg/rectifier could be out? Has anyone ever had this happen before?

Furthermore when the tank and stuff was off the bike last night we checked everything on the bike, hoses were all connected, carbs were correctly set in the manifolds, no fluid leaking, no electrical wiring off their connectors, nothing really....

Any suggestions on where to go next?
Thanks
Kiwi
 

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Hi guys,
well we spent a good part of 4 hours last night and here's what we did, all to no luck:

Removed tank
Removed air filter again
Removed top of carbs and pulled out the needles
Drove down to the hardware shop and bought a small washer for each carb/needle
Checked the diaphram for cut's/rip's(all in good condition)
Put the carbs back together again
Replaced(with new tubing) the vacum/carb tubes(after pulling all of them off and blowing through them all- they were fine- no cuts or tears in them)
Above the cam cover there is what looks like a reed valve/fuel filter item- removed this and cleaned it out, then put it back on again
Replaced the tank and air filter- went for a ride.... and the same issues still exists, however it did rev to about 9000rpm this time, however I think this may now be because we fitted the washers on the needles.

We were so frustrated, so then we put a voltage meter on the battery and found the following:

- At idle it's producing about 12.5volts
- At 3000rpms it's producing about 14 volts
- At 10000rpms(under no load) it's producing about 14.5 volts.

Maybe the reg/rectifier could be out? Has anyone ever had this happen before?

Furthermore when the tank and stuff was off the bike last night we checked everything on the bike, hoses were all connected, carbs were correctly set in the manifolds, no fluid leaking, no electrical wiring off their connectors, nothing really....

Any suggestions on where to go next?
Thanks
Kiwi
Did you check the float bowls and jets?
Do the carb slides rise and fall smoothly?
If there was something blocking the vacuum port in the carb that controls the slides they wouldn't lift as the vacuum dropped.
Are both pipes the same temp?
Have you added choke when the engine is warm and seen a change?

I'm still thinking there's a blockage of some kind in one or both of the carbs. Complete disassembly and cleaning may be next. I've had a carb from a small engine that needed to be cleaned/soaked 3 or 4 times before the blockage finally let go. And that's using an ultrasonic cleaner. Fuel filter in the tank on the end of the fuel line broke off and it sucked small particles into the carb.

Voltage is fine. Don't rev to 10,000 if you're not under load...


Jay
 
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