Carb problem?

[Carytowncat]

Hello,

I just posted my intro in the New comer thread if anyone wants to read.

I have a 2002 EX250 and it seems to frequently "bog out" when I open the throttle. If I open it up wide then it will push past the bog and wind right up after a few seconds.

I did a thorough carb cleaning... twice :O) but I did not set the float heights. Could this be the problem?




She has a brand new air filter, my petcock is working fine (When I remove the gas line and hit the starter fuel pours right out)

I also tried the propane check for vacuum leaks and didn't hear any change in RPM.

[Yarhj]

Disclaimer: I have no idea what's going on.

Also, before dealing with anything carb-related, I always have to ask -- did you manually clean out the pilot jet and pilot/transition circuit passages with some copper wire or something? Even if it doesn't look like something's clogged, if you don't scrub it, it may still not work (or may not work well).

With that out of the way, let's get to work! When you say it bogs out, specifically what happens? Does it just kind of do nothing -- no RPM increase? Do the RPMs actually drop a bit? Once you're past the bogging point, does it work perfectly normally in the higher rev range? Does it bog again if you close the throttle slowly, after getting past the bog initially?

My one thought is that the fuel/air mixture could be too rich at low throttle openings. If your spark plugs are black and sooty, that could support my half-baked hypothesis, but if you don't spend lots of time poking around at low revs there might not be much to see on the plugs.

Floats set too high could potentially do it, but I feel like that would impact the whole rev range (I'm not sure, though). If this was the case, the plugs would probably be black and sooty, since you'd be running rich most of the time.

What are your mixture screws set to? 2.5 turns out is a good starting point, but you could try tightening them each half a turn to lean the mixture out, and see if that helps.

Are you using stock jetting? I'm not sure there's any reason to change the pilot jet when mucking around with the carbs, but you never know what some previous owner might have done.

Also, have you checked out the diaphragms and the slides? If someone drilled the slides while installing a jet kit, it could cause a bog at low revs. If the diaphragms weren't sealing very well, or were cracked, or something, it might also do the same thing. Some pictures of what the slides look like before being drilled, and after, here.

ninja250.org has a nice little schematic showing the relative contributions of the different carb components at different throttle openings -- based on that I would say start with the mixture screws and see what happens. Here's a link to a nice guide on how to do that!

[Carytowncat]

Thank you for the response Yarhj,

OK, so let's say I shift into first and start off. Wind her right up to 8 grand, and then back off the throttle to shift into second gear, but as I open the throttle back up she looses all power as if it were running out of gas.


If I back off of the throttle she slowly regains her power and I can wind her back up.

And often if I just open the throttle without letting her wind up, power cuts right off and it feels like it is dying until I let off the throttle again and let it regain composure. lol

Is that information of any help?




Interesting suggestion about the air /fuel mixture screws. I did remove the caps and set those to 2 1/4, but I also missed with those on a ride trying to figure out a different problem. So I need to revisit those and check their position.

In that link you posted it mentions a whisker of Vaseline of grease around the diaphram to help seal it. Is that recommended? Also is that tiny hole a good safe mod? Because if I pull the carbs again I might just drill it. (and NO, she is not currently drilled there)

[flitecontrol]

Did you balance the carbs after you cleaned and installed them?

[Carytowncat]

Originally Posted by flitecontrol

Did you balance the carbs after you cleaned and installed them?

Is balancing setting the two butterfly flaps so that they are in sync? I did check those and they were set exact so I left 'em alone.

[Yarhj]

Well, now my guess is that it's either too rich or too lean. That narrows it down, huh? I'm still leaning a bit towards rich, but I wouldn't stake my lunch on it.

Are you backing the throttle all the way down to zero, or just relaxing it a bit while you shift? It may not have much to do with the mixture screws at all, unless you're dropping the throttle most of the way down when shifting. That said, try fiddling with the mixture screws and seeing what happens -- it's quick, and if it fixes the problem then there's no need to go hunting for anything else! If that doesn't work, you could check the float height.

It might be worth pulling the spark plugs out and seeing if they're black (rich) or white (lean), but it might be a good idea to have new spark plugs handy before you do that, since it's not the best practice to put the old spark plugs back in.

Originally Posted by Carytowncat

Thank you for the response Yarhj,
Also is that tiny hole a good safe mod? Because if I pull the carbs again I might just drill it. (and NO, she is not currently drilled there)

From what I've read, it's not a good idea, as it can make the throttle response a bit sluggish at low revs (and make it feel like it's bogging down, which is why I thought it might have been done to your bike), but I haven't done it myself.

Originally Posted by Carytowncat

Is balancing setting the two butterfly flaps so that they are in sync? I did check those and they were set exact so I left 'em alone.

When you balance the carbs you adjust them so they both get the same amount of vacuum. Check out this page for the procedure.

[Motofool]

Originally Posted by Carytowncat

...........I did a thorough carb cleaning... twice :O) but I did not set the float heights. Could this be the problem?..........

Your mix is lean in the middle-high range, reason for which the engine responds badly to more air (too much twist of the wrist).

If the symptom seems less pronounced when you keep the choke applied after warm up, the above statement is correct.

Low level of fuel can cause that.

Did you clean the little diaphragm and fuel filter by the left side of the carbs?
That is a fuel enricher to compensate for sudden throttle openings.
That filter goes unnoticed very frequently.

[Carytowncat]

Originally Posted by Motofool

Your mix is lean in the middle-high range, reason for which the engine responds badly to more air (too much twist of the wrist).

If the symptom seems less pronounced when you keep the choke applied after warm up, the above statement is correct.

Low level of fuel can cause that.

Did you clean the little diaphragm and fuel filter by the left side of the carbs?
That is a fuel enricher to compensate for sudden throttle openings.
That filter goes unnoticed very frequently.

Thank you for your guidance. I will check the choke tomorrow.

I did clean that little diaphragm and I am delighted to finally learn what it does!

There was no filter in my plastic fuel line though, and I cleaned those out well. I have however put 2 fuel filters in my line because of my tank being in such rough shape.

[Carytowncat]

Originally Posted by Yarhj

Well, now my guess is that it's either too rich or too lean. That narrows it down, huh? I'm still leaning a bit towards rich, but I wouldn't stake my lunch on it.

Are you backing the throttle all the way down to zero, or just relaxing it a bit while you shift? It may not have much to do with the mixture screws at all, unless you're dropping the throttle most of the way down when shifting. That said, try fiddling with the mixture screws and seeing what happens -- it's quick, and if it fixes the problem then there's no need to go hunting for anything else! If that doesn't work, you could check the float height.

It might be worth pulling the spark plugs out and seeing if they're black (rich) or white (lean), but it might be a good idea to have new spark plugs handy before you do that, since it's not the best practice to put the old spark plugs back in.



From what I've read, it's not a good idea, as it can make the throttle response a bit sluggish at low revs (and make it feel like it's bogging down, which is why I thought it might have been done to your bike), but I haven't done it myself.



When you balance the carbs you adjust them so they both get the same amount of vacuum. Check out this page for the procedure.

Thanks for your guidance. I think that I do back the throttle all of the way off when I shift.

I will recheck the air / fuel screws in the morning.

I am glad you mentioned the possible draw backs of modifying the slide. I am quite please with Kawasaki's engineering and will refrain from any mods unless absolutely guaranteed.

I am amazed at how in sync the system is, and those high RPMs are such a treat. Zing Zing!

My last real sport bike was a original F2 and I think it redlined around 7 grand.

[jkv45]

Because you said the tank was bad internally, I would start by completely cleaning it out. The petcock may need to be disassembled and cleaned also. Then add fresh 87 octane without ethanol if you can get it.

When you replaced the air filer, did you oil it?

The way it's acting makes me think the slides may not be rising and falling properly. I'd confirm they are at least moving freely by pushing them up with your finger and making sure they drop smoothly.

If you didn't carefully clean the jets and jet holder with a copper wire and carb cleaner, you need to.

What do the plugs look like?

What comes out when you open the float bowl drains? Anything unusual?

[Carytowncat]

Originally Posted by jkv45

Because you said the tank was bad internally, I would start by completely cleaning it out. The petcock may need to be disassembled and cleaned also. Then add fresh 87 octane without ethanol if you can get it.

When you replaced the air filer, did you oil it?

The way it's acting makes me think the slides may not be rising and falling properly. I'd confirm they are at least moving freely by pushing them up with your finger and making sure they drop smoothly.

If you didn't carefully clean the jets and jet holder with a copper wire and carb cleaner, you need to.

What do the plugs look like?

What comes out when you open the float bowl drains? Anything unusual?

Thanks JKV,

I did rebuild and clean the petcock. That is working correctly. I also checked the slides before putting it back in the bike, lifting 'em and letting 'em fall back down. They appear to be working smoothly and correctly.

I did clean the jets with carb cleaner, high pressure steam, and a tiny wire.

Have not checked the plugs yet and planned on doing so today but may be delayed because of rain.

I drained the float bowls yesterday and nothing unusual came out, just gas.

[agentbad]

Originally Posted by Carytowncat

Thank you for your guidance. I will check the choke tomorrow.

I did clean that little diaphragm and I am delighted to finally learn what it does!

There was no filter in my plastic fuel line though, and I cleaned those out well. I have however put 2 fuel filters in my line because of my tank being in such rough shape.

2 fuel filters might be overdoing it.

[Carytowncat]

Originally Posted by agentbad

2 fuel filters might be overdoing it.

I know, I was concerned they might be impeeding the flow but I removed the line and gas pours freely in abundance so that steered my thinking away from the filters. Also they are not gunky, only a tiny bit of debris at the first one which is only a screen filter.

Today was a whisker wet for me but I look forward to spending quality time with her tomorrow :O)

[Carytowncat]

Link to original page on YouTube.

[Carytowncat]

Hi,

I have my needle below the plastic spring holder, like in image A.
Is this correct?

[Carytowncat]

Oops! lol

Uhmm... so there is a vent tube that exits the middle of the carbs, that is supposed to just hang around doing nothing, but there is also a nice hole in the front of the air box... just about the size of the tube, so I figured ehhhh errrm... I mean they both ride the same bike and all... errrr


Well putting that tube into that air box hole produces the exact symptoms that I described above, and also relieves all of said symptoms when it is allowed to just dangle freely.

So there you have it *blushing*

Thanks for all of your guidance, it actually helped me eliminate many of the probabilities floating in my mind for long enough that I could see it was probably a vacuum problem.



I'm off for a Saturday ride. St. Christopher please be my guide