Jetting for a high float level?

HighPlainsSquid
Suppose your float level should be 8 mm or so.
Suppose it comes from the factory at, say, 6 mm. It's not overflowing, but this high float level will cause it to run rich.

The standard option is to adjust the float level to be correct. What's the difference between doing that and just jetting for the current float level?

Inquiring minds want to know.

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Paw Paw 271
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Paw Paw 271 3/3/2019 3:01pm
3/3/2019 3:01pm
That would be a bad aid instead of a fix.
Reset the float.

Paw Paw
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Hcallz5
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Hcallz5 3/4/2019 7:53pm
3/4/2019 7:53pm
Dude just set your float at the correct height. There's a spec for a reason. That is step one when setting up a carb.
BobPA
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BobPA 3/4/2019 8:33pm
3/4/2019 8:33pm
A high float level will not make it run rich, unless it is so high it is just dumping into the cylinder.
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kb228
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kb228 3/5/2019 6:00am
3/5/2019 6:00am
Its a lot easier to bend the tang than to rejet the whole carb... not sure why youd want to do that.
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HighPlainsSquid 3/5/2019 6:02am
3/5/2019 6:02am Edited Date/Time 3/5/2019 6:51am
Hcallz5 wrote:
Dude just set your float at the correct height. There's a spec for a reason. That is step one when setting up a carb.
It's mostly a hypothetical question. I like to understand "WHY?" and was just wondering if there would be any difference to the motor between more fuel in the bowl/leaner jet vs less fuel in the bow/fatter jet.

It's kind of like asking the question "What if I advance or retard my ignition timing?" Sure, there's a spec but what happens if I deviate from it a little? I see a LOT of talk about float bowl height on both KTMTalk and the KDX forum and was just curious about jetting to a different float level for whatever reason.
HighPlainsSquid 3/5/2019 6:32am
3/5/2019 6:32am
kb228 wrote:
Its a lot easier to bend the tang than to rejet the whole carb... not sure why youd want to do that.
On an '18 KTM 150 XC-W, I can rotate the carb and pop the drain and have a pilot jet in there and back together in less than 5 minutes, in the field. To change the float, thanks to the stiff rear boot, I have to remove the long shrouds that block the subframe, pull the subframe, remove the throttle slide, then open the carb and set the float. 30 minutes, start to finish.

BESIDES.... it's a hypothetical question. My float's correct. I was just wondering about it.
Layton
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Layton 3/5/2019 7:10am
3/5/2019 7:10am
Hcallz5 wrote:
Dude just set your float at the correct height. There's a spec for a reason. That is step one when setting up a carb.
HighPlainsSquid wrote:
It's mostly a hypothetical question. I like to understand "WHY?" and was just wondering if there would be any difference to the motor between more fuel...
It's mostly a hypothetical question. I like to understand "WHY?" and was just wondering if there would be any difference to the motor between more fuel in the bowl/leaner jet vs less fuel in the bow/fatter jet.

It's kind of like asking the question "What if I advance or retard my ignition timing?" Sure, there's a spec but what happens if I deviate from it a little? I see a LOT of talk about float bowl height on both KTMTalk and the KDX forum and was just curious about jetting to a different float level for whatever reason.
Jetting is precise as far a how much fuel is going into the engine. .
Having the float to high would mean there would be no control of exactly how much fuel is going into the engine.
barnett468
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barnett468 3/5/2019 8:13am
3/5/2019 8:13am
HighPlainsSquid wrote:
Suppose your float level should be 8 mm or so. Suppose it comes from the factory at, say, 6 mm. It's not overflowing, but this high...
Suppose your float level should be 8 mm or so.
Suppose it comes from the factory at, say, 6 mm. It's not overflowing, but this high float level will cause it to run rich.

The standard option is to adjust the float level to be correct. What's the difference between doing that and just jetting for the current float level?

Inquiring minds want to know.

Ok,at least I will answer your question for you. In general, the higher the float level, the richer it will run to some degree. This is because it takes less "force/vacuum" etc to "suck" the fuel up, the higher the level is.
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HighPlainsSquid 3/5/2019 12:38pm
3/5/2019 12:38pm
HighPlainsSquid wrote:
Suppose your float level should be 8 mm or so. Suppose it comes from the factory at, say, 6 mm. It's not overflowing, but this high...
Suppose your float level should be 8 mm or so.
Suppose it comes from the factory at, say, 6 mm. It's not overflowing, but this high float level will cause it to run rich.

The standard option is to adjust the float level to be correct. What's the difference between doing that and just jetting for the current float level?

Inquiring minds want to know.

barnett468 wrote:
Ok,at least I will answer your question for you. In general, the higher the float level, the richer it will run to some degree. This is...
Ok,at least I will answer your question for you. In general, the higher the float level, the richer it will run to some degree. This is because it takes less "force/vacuum" etc to "suck" the fuel up, the higher the level is.
Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets?

Can the engine tell if you've got more fuel/leaner jets vs less fuel/richer jets?

THAT'S my question! Smile
barnett468
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barnett468 3/5/2019 12:50pm
3/5/2019 12:50pm
HighPlainsSquid wrote:
Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets...
Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets?

Can the engine tell if you've got more fuel/leaner jets vs less fuel/richer jets?

THAT'S my question! Smile
"Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets?"

Not in general.


"Can the engine tell if you've got more fuel/leaner jets vs less fuel/richer jets?"

I'm guessing by "more fuel" you mean a higher float level etc. If so, then, yes, to some degree it can for lack of a better phrase.


"THAT'S my question!"

That is TWO questions and you should have asked them in the first place.

.
Moto Obsessed 3/7/2019 6:08am
3/7/2019 6:08am
HighPlainsSquid wrote:
Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets...
Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets?

Can the engine tell if you've got more fuel/leaner jets vs less fuel/richer jets?

THAT'S my question! Smile
Just thinking out loud here... If someone was doing mostly WFO riding on a big bore out on the salt plains, would that be a scenario where you'd want more fuel in the bowl to help keep up with the consumption?
dkurtd
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dkurtd 3/7/2019 7:57am
3/7/2019 7:57am
In the old days when we ran methanol in our Modified Midget 250's we would not only increase the bowl size by welding an extension on the side but we would also run different needle and seats (larger) to increase flow into the bowl. I don't however remember ever trying to run a higher float level to compensate for fuel flow or to richen the jetting. We ran almost double the size of jetting for methanol over race gas.
lcgordon711
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lcgordon711 3/14/2019 10:44am
3/14/2019 10:44am
Does anybody else struggle with adjusting the float height. For me it is so hard to see in where the plunger is and get the needle in the right position to measure. Seems like my first try always I do it wrong and no fuel goes into the carb so I have to take it back apart and do it again. It always frustrates me.
kb228
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kb228 3/14/2019 10:51am
3/14/2019 10:51am
lcgordon711 wrote:
Does anybody else struggle with adjusting the float height. For me it is so hard to see in where the plunger is and get the needle...
Does anybody else struggle with adjusting the float height. For me it is so hard to see in where the plunger is and get the needle in the right position to measure. Seems like my first try always I do it wrong and no fuel goes into the carb so I have to take it back apart and do it again. It always frustrates me.
If you hook up a tube and blow into your fuel inlet, it should seal when the seam on your floats are parallel to the gasket surface. Shouldnt be more complicated than that.
1
HighPlainsSquid 3/16/2019 7:01am
3/16/2019 7:01am
HighPlainsSquid wrote:
Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets...
Yeah, I know that.... but is there ever a situation where you would _deliberately_ run more fuel in the bowl and then _deliberately_ use leaner jets?

Can the engine tell if you've got more fuel/leaner jets vs less fuel/richer jets?

THAT'S my question! Smile
Moto Obsessed wrote:
Just thinking out loud here... If someone was doing mostly WFO riding on a big bore out on the salt plains, would that be a scenario...
Just thinking out loud here... If someone was doing mostly WFO riding on a big bore out on the salt plains, would that be a scenario where you'd want more fuel in the bowl to help keep up with the consumption?
There!!!! That's what I was looking for... are there any cases where you MIGHT want to _deliberately_ do this thing? Conversely, if you were riding slowly over very bumpy terrain all the time, might you lean the bowl a bit? I was just curious. To me, it's like messing with ignition timing... there are cases where you might deliberately advance or retard timing, ya know?
1
HighPlainsSquid 3/16/2019 7:03am
3/16/2019 7:03am
lcgordon711 wrote:
Does anybody else struggle with adjusting the float height. For me it is so hard to see in where the plunger is and get the needle...
Does anybody else struggle with adjusting the float height. For me it is so hard to see in where the plunger is and get the needle in the right position to measure. Seems like my first try always I do it wrong and no fuel goes into the carb so I have to take it back apart and do it again. It always frustrates me.
kb228 wrote:
If you hook up a tube and blow into your fuel inlet, it should seal when the seam on your floats are parallel to the gasket...
If you hook up a tube and blow into your fuel inlet, it should seal when the seam on your floats are parallel to the gasket surface. Shouldnt be more complicated than that.
I like to do that ANYWAY because it really helps reveal any leaks. I submerge the whole carb in a bucket of gas or kerosene (outside!!!!) and blow into the tube while closing the float. If there's a gasket leak in the carb, you'll see it.
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Paw Paw 271
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Paw Paw 271 3/16/2019 11:23am
3/16/2019 11:23am
Just reset the float correctly.

PawPaw

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