More Carb help

[Clyde K.]

Gennelmen an Gurus. I stand here, with hat in hand, and beg your indulgence. I have put new floats in my carbs and set them to 25.7 and still wipe out spark plugs. I finally remembered to use clear fuel line and gauge by sight where I stand. My fuel levels are currently above the lip of the body on all 4 carbs. If I remember right they need to be just about where the bowl screw heads contact the bowl. Right? My quandary is: Which way do I adjust, and how much? Bare in mind that I'm a (re)tired ol' mud Marine with little or no concept of "mms" or "thousandths" and easily confused. I'm more familiar with measurements like 27 and an RCH or 24 and half a frog hair (or "right 2, up 1, FIRE"). Any help would be appreciated.

[3Phase]

Clyde,

If you've got the brass floats and float needles with no rubber tips, use some Brasso to polish the needles and seats to fit each other. Try not to mix 'em up after that.

Don't mess with the floats, just make sure they're squared away high and tight then put the carbs back on and check the fuel levels again.


Now listen up and pay attention: The clear tube fuel level check is done with the engine running! If you tried to check the fuel levels in any other way that caused the engine to not be running -- wrong answer!

Hook up a tube, start the engine and look at the fuel level while you work the throttle. The fuel level will drop a RCH or two but she'll come right back up for ya, then settle down easy while the engine idles.

That right there's your fuel level.

If it's too high or too low, pull the carbs again and raise or lower the floats a couple of micro 'klicks and as many FFH as you need.

When you get it right, "FIRE!"

"REPEAT!"

OOSHAA!

Oops, that's Army Redlegged gunbunnies....

.

[Clyde K.]

Ooopppsss

Thanks 3Phase. The scoot has been running like crap since I installed the new floats so in keeping with XS11 protocols I took the carbs back off to clean, clean, clean and remeasure the float level. As stated previously, I set the floats at 25.7 and they still flooded. A recheck on the float level showed that they were still at 25.7 so I looked for something else. Following the tech article by Ken Talbott, I set the carbs up in the vise, put the gas tank on a shelf above and used some of my wife's discarded oxy tubing to connect it all up and found my problem. Now I need HELP to determine which direction to go (more or less float height) to resolve my problem as too many "jumps without a helmet" prevent in depth analysis (I'm sure my "Dog Face" friends understand ). OOORAH!

[Clyde K.]

Thanks 3Phase. The scoot has been running like crap since I installed the new floats so in keeping with XS11 protocols I took the carbs back off to clean, clean, clean and remeasure the float level. As stated previously, I set the floats at 25.7 and they still flooded. A recheck on the float level showed that they were still at 25.7 so I looked for something else. Following the tech article by Ken Talbott, I set the carbs up in the vise, put the gas tank on a shelf above and used some of my wife's discarded oxy tubing to connect it all up and found my problem. Now I need HELP to determine which direction to go (more or less float height) to resolve my problem as too many "jumps without a helmet" prevent me from making an accurate in depth analysis (I'm sure my "Dog Face" friends understand ). OOORAH!

[WMarshy]

Where the new floats you installed made of brass or were they plastic? There is a different measurement based on material.

[motoman]

Thanks 3Phase. The scoot has been running like crap since I installed the new floats so in keeping with XS11 protocols I took the carbs back off to clean, clean, clean and remeasure the float level. As stated previously, I set the floats at 25.7 and they still flooded. A recheck on the float level showed that they were still at 25.7 so I looked for something else. Following the tech article by Ken Talbott, I set the carbs up in the vise, put the gas tank on a shelf above and used some of my wife's discarded oxy tubing to connect it all up and found my problem. Now I need HELP to determine which direction to go (more or less float height) to resolve my problem as too many "jumps without a helmet" prevent me from making an accurate in depth analysis (I'm sure my "Dog Face" friends understand ). OOORAH!

You didn't say, but I'm presuming gas was leaking by the float needles with your test.
Brass floats, your initial setting would be correct. If you swapped to fiber floats, then I'm guessin' 23mm would be closer to correct.
From what I've seen on here, the early carbs are more forgiving, not only tuning, but more fuel level 'friendly' since having the cross-over tunnel feeding BOTH circuits ALL the time seems to compensate for minor setting-up and tuning errors.

[Clyde K.]

WMarshy -- Brass floats. Brant -- I don't think that fuel is getting by the float needle. I believe that the problem is that the 25.7mm setting is too high or my micrometer is way off. I use a slide mic set at 25.7. The foot (long rod) goes on the FLAT surface of the carb body closest to the float and clearance is checked at the end of the scale (all 8 floats are measured to ensure accuracy). I will just have to reset one to 25 and see where the level ends up. Once I find the correct setting I'll record it in my manual for posterity. Has anyone else battled this devil or is 25.7mm (or 23mm) just a rule of thumb, or starting point (similar to the bench sync exercise)?

Maybe my floats were from a batch of "Seconds", or my wife put a curse on them so I could never get it running well enough to ride, who knows? At any rate, thanks to all for the input/advise, again. Semper Fi

[cajun31]

Clyde

Give more details on what all you have done. Did you change the floats because the old ones were bad? Did you change all of them or just bad ones? Were any other changes made? Did you totally disassemble the carbs from the rack when you cleaned them or just remove the caps and bowls? When you say you are wiping out the plugs... running or just at idle?

[motoman]

Hey Clyde,
Before Greg jumps me again, I might get the chance to run over there and have a look at what you got goin' on before we 'cage' it to GA. next Mon.

[3Phase]

Clyde,

It doesn't really matter what type of floats you have except for the initial float height setting. The fuel level in the float bowls is ~3mm (+/- 1mm). The float height settings and fuel levels are similar to Battle/Bore Sight Zero and should get you on the target so you can adjust and tune from there until it's dialed in.

The fuel level is supposed to be measured from the carburetor body down onto the float bowl and should put the fuel level close to the lock washer or the screw head.

Here's a link to XJBikes.com with a color picture in Post #5:-

Wet Set...Can Somebody Check My Work?

Carry on!

.

[bikerphil]

If you set the brass floats at 1" by eye with a small ruler, all 8, that should be correct for the early style carbs. Set the bank upside down with no gaskets, measure to highest part of float bulb. It is important to have them all identical so be methodical. This is how I do them and it works every time, YMMV

[Clyde K.]

It lives!!!!

3Phase, thanks for the confirmation/nudge with the battle sight zero comment. I guess I have had too many shots to the head without a helmet as any more, I am just anal enough to not accept anything less than what I'm told, i.e., 25.7 IS 25.7 (what the heck does "~3mm" mean anyway). The article you linked to was basically the same as I what I had used from the XS11 tech site. I got the levels to the screw head and washer (roughly 1/4" lower than they had been) and measured. It ended up being 27-27.3 in my case. Runs great, Thanks all.

Are any of you guys old enough to remember when Marines were called "Jar Heads", Army were "Dog Faces", Navy were "Swab Jockies" and Airmen being "Wing Wipers"? I hope that everyone understands that I mean no offense if I slip now and again. Semper Fi.

[motoman]

Glad to hear you resolved the problem Clyde!

The 3mm down from the carb upper body is the way the fuel levels are gauged on the 81's and XJ's using a clear hose attached to the nipple of the fuel bowl, and a seating side screw is located on lower end of sides of all the bowls. These were the only models that used this process, hence the reason for the nipple and seating drain screw.
The 80 models used the 23mm static float level setting, which again is different from the 78-79 float settings, as you correctly allured to initially.

[3Phase]

You're welcome, Clyde, glad to see you got it running!

~3mm is just another Metric Mosquito Wing sticking its tongue out at the fresh raw and fat 2/17" recruits but it's still got a lot to learn from the leaner and meaner 3/16" troops.


Operator head space and timing: have you set the valve clearances and checked the camshaft and ignition timing?

Like adjusting a multi-barrel gun cluster or a Gatling, after you get to fire you're supposed to adjust it. The carburetor float and fuel level specs all have a range that's for everything from a new engine sitting on the assembly line to a used engine that's not totally toasted.

If you've got an exhaust 'scope or you've somehow become really good at reading spark plugs you can set the fuel levels for the individual cylinders instead of the default Four Musketeers, "All for one and one for all!"

.

[Bonz]

Point of order here...

Shouldn't the float height be set with the carb bank at an angle so the tang just touches the needle spring, but does not compress the needle spring?

At least that is how I have done it based on instruction from folks that know more about this stuff than I do.

When the carbs are turned completely upside down to measure float height, that is a lot of weight from the float, relatively speaking, compressing the tang into the needle spring nub.

Ok, let the beatings begin...