Flooding Engine at Low Throttle

[xaple]

My bike is completely stock, no adjustments have been made.

When I start up the bike I get a nice good idle, and when I turn the throttle fairly fast the bike responds well.

If I slowly turn the throttle the engine seems to run super rich and flood. My spark plugs are very black.

I suspect it is flooding because when the choke is on and i slowly give it throttle I get the same result, also when I slowly give it throttle and it starts to bog down the idle drops really low and either stalls or recovers. Once the bike stalls I can not get it to start back up again unless I hold the throttle open max.

What could cause the bike to all of a sudden run so rich that it floods.

[subxero]

this is when the bike is fully warmed up with out the choke on correct? (sorry have to ask)

and you have not adjusted or turned a single thing on the bike since you received it and it ran fine then correct?

how many miles?

first check all your vac lines ect... make sure they are tight and connected, make sure choke is working properly, then I would check the filter make sure it is clean and air flow is normal, then open up the both sides of the carb just to make sure everything is in place and good.

After all of that and you don't find any issues then IDK take it to a shop

[xaple]

Originally Posted by subxero

this is when the bike is fully warmed up with out the choke on correct? (sorry have to ask)

and you have not adjusted or turned a single thing on the bike since you received it and it ran fine then correct?

how many miles?

first check all your vac lines ect... make sure they are tight and connected, make sure choke is working properly, then I would check the filter make sure it is clean and air flow is normal, then open up the both sides of the carb just to make sure everything is in place and good.

After all of that and you don't find any issues then IDK take it to a shop

Compression checked, valve clearance checked, air filter checked,, tried it without a filter as well.
10k miles, carbs are synced, all hoses are checked.

The problem is isolated in the carburetor because I was able to swap out a friends carbs with mine and it ran fine, I then swapped out the slides, diaphragm, main jet, and pilot jet. The problem was still there, So it isn't any soft parts, I'm out of ideas and I feel like the damn dealer is going to say I need new carbs.

[subxero]

did you check your floats, the jets did not turn out? (it happens)

Seems like you covered lots of the angles and have it narrowed down, I would just clean the carb good, make sure nothing is leaking ect...


good luck

[alex.s]

the internal fuel line leading to your pilot jet is partially clogged. soak the disassembled carb in cleaner and run seafoam through the pilot system. its also possible your float height needs fine adjusting..

[Motofool]

Originally Posted by xaple

...............The problem is isolated in the carburetor because I was able to swap out a friends carbs with mine and it ran fine, I then swapped out the slides, diaphragm, main jet, and pilot jet. The problem was still there, So it isn't any soft parts, I'm out of ideas and I feel like the damn dealer is going to say I need new carbs.

I have been following your previous threads and it seems to me that the operation of the float valves has been overlooked.

It seems that the bowls are having progressively lower level until the carbs starve.

Keep that siphon installed for each carb while the engine runs and observe the level.

[xaple]

Originally Posted by alex.s

the internal fuel line leading to your pilot jet is partially clogged. soak the disassembled carb in cleaner and run seafoam through the pilot system. its also possible your float height needs fine adjusting..

I boiled them and saw a lot of gunk come out hat i wasn't able to get out before, I guess now I will soak them in cleaner and double check the float height again.
How this cause it to run rich and not lean?

[xaple]

Originally Posted by Motofool

I have been following your previous threads and it seems to me that the operation of the float valves has been overlooked.

It seems that the bowls are having progressively lower level until the carbs starve.

Keep that siphon installed for each carb while the engine runs and observe the level.

Is that hooked up to the drain port? Could I use a plastic clear tube to test the height by hooking it up to that?
Just seems odd that it is showing symptoms of being rich and flooded and having too low of a fuel level would make it run lean no?

I just measured the levels and the left bowl was 22mm above the bottom of the carb body and the right one was 2mm under. I'm guessing this has to do with he bike being on the kickstand? Still seems very high for being on the kick stand, Could the bowls having too much fuel cause this to happen? seems like an irreverent problem if the fuel is still metered by the jets.

[Motofool]

Originally Posted by xaple

Is that hooked up to the drain port? Could I use a plastic clear tube to test the height by hooking it up to that?
Just seems odd that it is showing symptoms of being rich and flooded and having too low of a fuel level would make it run lean no?

Yes and yes (just don't use a silicone tube: gas will eat it up).

It could be rich first and then lean, if the level is too high first and then too low.
I don't know for sure, it is just a suggestion for something else to verify.
You could have a combination of problems.

The Ventury effect can only lift so much column of fuel and make it go through the orifice of the jets and needles.
So jets and level are basically working together to achieve a precisely metered flow of fuel into the stream of incoming air.
Low level = less fuel and vice-verse.

I assume that you have cleaned every internal passage of the carbs, including the idle circuit and the adjusting screws and O-rings.

[xaple]

Originally Posted by Motofool

Yes and yes (just don't use a silicone tube: gas will eat it up).

It could be rich first and then lean, if the level is too high first and then too low.
I don't know for sure, it is just a suggestion for something else to verify.
You could have a combination of problems.

The Ventury effect can only lift so much column of fuel and make it go through the orifice of the jets and needles.
So jets and level are basically the same things.

I assume that you have cleaned every internal passage of the carbs, including the idle circuit and the adjusting screws and O-rings.

Yeah I cleaned the hell out of this thing, everything that can be removed without throwing off the main body's alignment was removed, all of the tubes and holes were checked.

Its just so confusing how replacing My pilot, main jets, diaphragms, caps with ones that were verified to work still causes mine to not work...

[xaple]

Originally Posted by Motofool

Yes and yes (just don't use a silicone tube: gas will eat it up).

It could be rich first and then lean, if the level is too high first and then too low.
I don't know for sure, it is just a suggestion for something else to verify.
You could have a combination of problems.

The Ventury effect can only lift so much column of fuel and make it go through the orifice of the jets and needles.
So jets and level are basically working together to achieve a precisely metered flow of fuel into the stream of incoming air.
Low level = less fuel and vice-verse.

I assume that you have cleaned every internal passage of the carbs, including the idle circuit and the adjusting screws and O-rings.

Just put the bike on the stand and put it level as possible, the readings come up at around 8mm above the carb bodies lowest point which is troubling. I figured if it really is flooding and opening the throttle slowly causes there to be way too much gas for the engine to handle then by turning the idle adjustment knob on the side far enough the engine should rev up until the butterflies are opened enough for the flooding carbs to let all the gas in.

When I turned the knob it revved to abut 3k and after more turning the idle dropped to under 1k and would not take even a hint of throttle movement. This makes me believe that there is definitely way too much fuel in the bowls and it is flooding out into the carb and opening the butterfly slighly causes the engine to have way to much fuel but when i pound the throttle open it is able to compensate.

When I slam the throttle open it also hangs on its way down to idle so it is definitely rich.

Hopefully this is it...

[alex.s]

i believe your conclusions on why it is rich are misguided.

[alex.s]

the choke not effecting it gives the answer away.


adjust your float heights.

[Motofool]

Originally Posted by xaple

..........
Hopefully this is it...

These may not apply to your new-gen bike, but are good reference:

http://faq.ninja250.org/wiki/How_do_..._the_floats%3F

http://forums.ninja250.org/posting.p...&t=85429&tro=1

[jkv45]

Originally Posted by xaple

I boiled them and saw a lot of gunk come out hat i wasn't able to get out before, I guess now I will soak them in cleaner and double check the float height again.
How this cause it to run rich and not lean?

If you saw a lot of junk come out when you cleaned them there's a good chance there's more stuck somewhere.

Did you blow the passages out with high pressure compressed air?

At this point I would soak the entire carb in cleaner, and possibly have them ultrasonic cleaned.

It's possible the needles aren't seating properly - I'd replace them at this point. When you have the carbs off and turn them upside-down you should feel the needle seat before the float bottoms on the carb body. If that's not happening they might not be shutting the fuel off completely.

[Runeknight95]

Originally Posted by xaple

I boiled them and saw a lot of gunk come out hat i wasn't able to get out before, I guess now I will soak them in cleaner and double check the float height again.
How this cause it to run rich and not lean?

What did ya boil?

we swapped everything in my carbs to yours except the floats, who the hell knows :\

[xaple]

Originally Posted by Runeknight95

What did ya boil?

we swapped everything in my carbs to yours except the floats, who the hell knows :\

I literally took all the jets and soft parts out and put the entire thing in boiling water. After I took them out i sprayed them down with carb cleaner so the water didn't sit.

The literal last thing that could be wrong is that the floats are not working correctly or maladjusted. There is no arguing the bike is running very very rich at low rpms. There's nothing else i can think of.

The only part we didnt swap out was the mix screws and the floats. I know it's not the mix screws because my idle is perfectly fine.

[xaple]

Originally Posted by jkv45

If you saw a lot of junk come out when you cleaned them there's a good chance there's more stuck somewhere.

Did you blow the passages out with high pressure compressed air?

At this point I would soak the entire carb in cleaner, and possibly have them ultrasonic cleaned.

It's possible the needles aren't seating properly - I'd replace them at this point. When you have the carbs off and turn them upside-down you should feel the needle seat before the float bottoms on the carb body. If that's not happening they might not be shutting the fuel off completely.

If I try and blow air through the fuel hose and push the bowls up manually it stops the air from coming through. So would that indicate that they are working?

When I set up a funnel as a gas tank, I did notice the gas was leaving the funnel rather quickly. Much too quickly for a bike at idle. I also notice there is a lot of gasoline in the carb and the rubber engine headers. And I think there is gas in the air box because my air filter smelled of gasoline. I'm not sure if this evidence is conclusive or not but it gets me thinking.

[Runeknight95]

Originally Posted by xaple

I literally took all the jets and soft parts out and put the entire thing in boiling water. After I took them out i sprayed them down with carb cleaner so the water didn't sit.

The literal last thing that could be wrong is that the floats are not working correctly or maladjusted. There is no arguing the bike is running very very rich at low rpms. There's nothing else i can think of.

The only part we didnt swap out was the mix screws and the floats. I know it's not the mix screws because my idle is perfectly fine.

And you saw extra ****?

Hey btw put new plugs in, bike is running great!
Why would plugs die at 2k miles wtf?

[xaple]

Originally Posted by Runeknight95

And you saw extra ****?

Hey btw put new plugs in, bike is running great!
Why would plugs die at 2k miles wtf?

No idea haha, I knew something was funny. I was 100% sure I put everything back the right way, and the battery was cranking the starter. Maybe plugs have a shelf life and just have to be replaced after a certain amount of time.

[Lychee]

how much would it cost to replace the carb with a used one?

[xaple]

Originally Posted by Lychee

how much would it cost to replace the carb with a used one?

Haven't really looked into this, I know new ones are like 1000$ from online.

[jkv45]

Originally Posted by xaple

If I try and blow air through the fuel hose and push the bowls up manually it stops the air from coming through. So would that indicate that they are working?

I think it would.

But you mean push the floats up manually, right?

If you are at the end of your rope, I'd pull the carbs and take them to someone that knows carbs. Explain the issues and what you have done, and let them clean them and replace what they think is necessary. I don't think you need to buy a new set to cure the problem. They shouldn't be junk, but there has to be a problem somewhere...

[xaple]

Originally Posted by alex.s

the choke not effecting it gives the answer away.


adjust your float heights.

Just Adjusted the float heights and my fuel level is about .7mm below the mating surface of the bowl. No improvement.

[Motofool]

If you keep that siphon installed for each carb while the engine runs, can you see any fluctuation of that level?

[xaple]

Originally Posted by Motofool

If you keep that siphon installed for each carb while the engine runs, can you see any fluctuation of that level?

No it stays consistent.

[Motofool]

OK, at least you have eliminated another variable.

Next, do you see the choke cable releasing the choke plunge all the way, with some slack at the end?

Are the choke slides free for the plunge to close the fuel by-pass completely?

[xaple]

Originally Posted by Motofool

OK, at least you have eliminated another variable.

Next, do you see the choke cable releasing the choke plunge all the way, with some slack at the end?

Are the choke slides free for the plunge to close the fuel by-pass completely?

Yeah I double checked the choke and made sure it was sealed up correctly.

[Motofool]

Originally Posted by xaple

Yeah I double checked the choke and made sure it was sealed up correctly.

I have run out of ideas ............

[xaple]

Originally Posted by Motofool

I have run out of ideas ............

I been grasping at straws for the past week... I feel like if I take it in they are going to charge me $85 and say they don't know what it is.

[Motofool]

Originally Posted by xaple

I been grasping at straws for the past week... I feel like if I take it in they are going to charge me $85 and say they don't know what it is.

They sure will, ........if we don't know, how could they?
Nobody will take the time and interest that you can.

What you have mentioned before had me thinking:
At 10K rpm and WOT, the demand of fuel is around 2 cc per second.
Your funnel was going down fast and then there was a lot of fuel around the boots and intake box.

When carbs don't hold the level because a float is punctured or because the valve has hardened (and the petcock is defective), fuel can keep flowing slowly and steadily into the crankcase via the intake valves and rings, ruining the oil and filling the crankcase cavity up.

When intake valves don't close properly, there is a back flow in the Venturi of the carb(s) that can blow fuel backwards into the air filter and intake box.

When the crankcase is not opened to the atmosphere, the pulses of pressure from the moving pistons can push oil out (an into the inbox, at least in the case of a stock pre-gen).

Just throwing ideas to you, nothing solid or coherent.
I still don't trust those float valves of your carbs.

[xaple]

Originally Posted by Motofool

They sure will, ........if we don't know, how could they?
Nobody will take the time and interest that you can.

What you have mentioned before had me thinking:
At 10K rpm and WOT, the demand of fuel is around 2 cc per second.
Your funnel was going down fast and then there was a lot of fuel around the boots and intake box.

When carbs don't hold the level because a float is punctured or because the valve has hardened (and the petcock is defective), fuel can keep flowing slowly and steadily into the crankcase via the intake valves and rings, ruining the oil and filling the crankcase cavity up.

When intake valves don't close properly, there is a back flow in the Venturi of the carb(s) that can blow fuel backwards into the air filter and intake box.

When the crankcase is not opened to the atmosphere, the pulses of pressure from the moving pistons can push oil out (an into the inbox, at least in the case of a stock pre-gen).

Just throwing ideas to you, nothing solid or coherent.
I still don't trust those float valves of your carbs.

So what should I try to replace? The float itself or the little plunger, or something down inside the hole?
Also how could this part have gone bad? Seems just like a piece of rubber that's pushed in to a hole.

[Motofool]

Originally Posted by xaple

So what should I try to replace? The float itself or the little plunger, or something down inside the hole?
Also how could this part have gone bad? Seems just like a piece of rubber that's pushed in to a hole.

No, I wouldn't replace anything until you find the root of the problem.
Besides, if the fuel level is kept within spec for each carb while the engine is working and acting up, those things are working properly.

Again, I was just thinking aloud.

[alex.s]

so, its fine when you wot but not so fine when you slowly pull back. the fuel height is fine, the carb is thuroughly cleaned, it has correct sized jets, the choke is not engaged (does the choke work? when idling and you pull the choke, it jumps to 4krpm right?), there are no vacuum leaks (did you test this? hair spray or carb cleaner- spray it near the carbs or something if the bike jumps up its pulling from the air which means vacuum leak), the diaphram is seated correctly and not torn.... what about the needles? are the needles perfectly straight? what about the slides? maybe you could lubricate the slides? are you sure theres no leak in the diaphram?

[alex.s]

are the carbs boots actually properly clamped down to the head

[xaple]

Originally Posted by alex.s

so, its fine when you wot but not so fine when you slowly pull back. the fuel height is fine, the carb is thuroughly cleaned, it has correct sized jets, the choke is not engaged (does the choke work? when idling and you pull the choke, it jumps to 4krpm right?), there are no vacuum leaks (did you test this? hair spray or carb cleaner- spray it near the carbs or something if the bike jumps up its pulling from the air which means vacuum leak), the diaphram is seated correctly and not torn.... what about the needles? are the needles perfectly straight? what about the slides? maybe you could lubricate the slides? are you sure theres no leak in the diaphram?

What can I lubricate the slides with? That would make sense if they aren't opening with low pressure but when you give it heavy throttle its able to lift.
Needles are straight.

Originally Posted by alex.s

are the carbs boots actually properly clamped down to the head

Yeah they are, the most confusing part is that putting someone else carbs in made it run fine and replacing all the replaceable parts in mine with his did not make it run good.

[jkv45]

I'm still thinking there is an internal blockage somewhere - like one of the passages controlling the vacuum/pressure to the CV diaphragms.

With an abrupt change in throttle position you are getting some amount of vacuum/pressure, but with the blockage a small change in throttle position isn't lifting the slides because of the obstruction.

That's about all I can think of that would cause what you described.

[alex.s]

i don't think you're actually supposed to lube the slides. maybe spray them with carb cleaner, but do they move freely?

[Motofool]

Yes, Alex, OP has videos of the needles going up when they feel the vacuum of the engine (another thread).

Originally Posted by xaple

........
When I start up the bike I get a nice good idle.....

when I turn the throttle fairly fast the bike responds well.

If I slowly turn the throttle the engine seems to run super rich and flood.
.....
when the choke is on and i slowly give it throttle I get the same result.....

when I slowly give it throttle and it starts to bog down the idle drops really low and either stalls or recovers.

Once the bike stalls I can not get it to start back up again unless I hold the throttle open max.

As over-rich mix only happens when the butterfly is opened and sustained engine vacuum reaches the Ventury, IMHO, it must be either those float valves that fail with vibration (temporarily flooding one or both bowls) or a case similar to that old thread where the guides of the needle were missing.

It seems to me that the oil should be contaminated with fuel at this point.

Maybe @choneofakind could remember if these symptoms could be related to enlarged P compensation holes in the slides.

[choneofakind]

Nope, at least not that I ever experienced. The only symptoms I got from enlarged slide holes was a funky stutter at 6k during constant throttle.