Float bowl tabs; bad tab, bad, bad...

So I'm finally adjusting the float level in the Mikuni BS34 carbs for the XJ1100. I have replaced all the float valves & seats. I line up the carbs on a jig & check the level & make sure they're level in all directions by using a bullesye level on top of the carbs (putting a large washer around the nipple on top of the carb so the bullseye rests flush) and then do the sight gauge check using a tube marked with two lines 3mm apart. I place the upper line where it shows in the manual (3mm below from the carburetor mixing chamber body edge). The levels are horrendous.

Here's how I leveled the carbs:

Carbs on the jig. Note the bulls eye level with washer below on top of #2 carb


How I adjust so the bulls eye level is centered (the rear two feet are also bolts and are adjustable)


How the bulls eye level looks before leveling


What the bullseye looks like when the carbs are made level.


I'm finding some of the fuel levels to be as much as 7-8 mm too high in the sight tube. It says in the manual to slightly bend the tab to adjust the float level. All of the tabs were almost parallel with the metal connected to the floats. It was hard to get anything in there to bend the tab but finally I did, The metal is pretty thick and does not want to bend. Finally after bending the heck out of the tabs I get the level to be 3mm below the carb mixing chamber edge as shown in the manual.

Problem is the manual says to bend "slightly" the tab & I've had to really bend them way down, it's almost like the valve should have been 1mm or so longer instead.

Now I'm to the last float to do and have had to really bend these tabs way down. They're so stiff I really don't want to bend this last one any further and I'm still 3mm too high on the fuel level. I'm thinking I'll have to actually bend the flat plates attached to the floats themselves if I'm going to lower the fuel level these last 3mm.

Doesn't make sense to me. Any ideas?

 

The rack should be level across the 4 but angled forward as they are orientated when on the bike, could make a big difference.

 

Yep, I measured mine to be 7-8 degrees forward, and got confused again..

 

i have found that placing the carbs on a smooth and flat surface and aligning the floats to level with the surface of the carbs made it so that i didnt have to adjust the float but to a minimum.. that way you know the needle valve is seated and the floats are equal, some will disagree with this assessment but all i have to say is i have no problems with too much or too little fuel and no leaks.. so theres my lil bit and take it or leave it.

 

The factory spec calls for them to be set with the carbs level in all directions.

Yamaha knew they were "tipped" forward when on the bike, but they still specified level-level, and the book goes to great lengths to explain how to get the bike propped up so the carbs are level even when on the bike.

You want to hold your clear tube up as close to the center of the side of the carb as possible for a more accurate reading.

Huge adjustments like that are generally the result of aftermarket needles and seats being a couple mm different from OEM, or worn float pivot holes.

This is one instance when "dry setting" beforehand would help get you into the ballpark more quickly than JUST the clear tube. Think of dry setting as the bench sync, then do your real-world "fine" adjustment using the clear tube.

 

It does seem like the valve is a tiny bit shorter, the part held by the tab. The manual (pages 4-6 through 4-8 only describes clear tube adjusting with the carbs on the bike and I can't find any specs for a dry setting. I did find mentions of 23mm from the top of the float to the flat part of the body as dry settings for the older XS1100 carbs. I wasn't able to find anywhere via manual or forum consensus that says what the proper level for the XJ1100 is.

I'm kinda stymied at what to do at this point.

 

can you post pics of the tab and needles?

 

Just got them.

Before I started bending the tab, the tab was just about flat with the hinge plate. This just seems to be way too much bend from what it was made with 30 years ago..

Lateral float & notice how much the tab has had to be angled. I still need to bend it more to lower the gas in the sight tube more 3mm.
(Fuzzy look at the XJ1100 in the background).



Float hinge/tab from above



float needles. The lower one is the new one. I probably could have reused the old ones but with 30 year old rubber I thought it best to replace them. Lengthwise they look the same. A different clip but that's not the part that is pushed by the tab.


I'm stuck right now, thought I'd be quickly done with carb everything & I'd be off to other areas that need attention. Don't want to have to remove these carbs this year, they're a !@#$% to get out of the bike.

 

thanks for the pics. Well I have a smaller displacement bike but my tabs are bent about that much too. let's see what the guru's think. BTW the pics are worth a thousand words.

 

Thanks for the suggestions thus far.

When I read the manual on fuel level measurement (page 4-5) it says: "Adjust the motorcycle position by placing a suitable stand or a garage jack under the engine so that the carburetor is positioned vertically".

The way I interpret that is that the carbs are supposed to be checked when level as they were on the jig I made when I had the carbs resting square at 90 degrees. Perhaps I am misunderstanding the words and that's not what they meant. Assuming they didn't mean the carbs should be 90 degrees to level I balanced the bike and then measured the resting angle the carbs sit in the manifolds using a flexometer to the back of the carbs & they're tipped forward at 5 degrees. I'll set the jig with a 5 degree forward tilt & check how the sight level relates to what it was before.

It also says "Start the engine and stop it after a few minutes of run. This procedure is necessary to obtain the correct fuel level". That sounds like the idea is to run fuel through the float bowl. Since the only thing the sight tube measures is gas height in the float bowl, perhaps the reason to run fuel through it is to purge air from the bowl? What makes sense to me is if I run fuel into the carb & drain it through the float bowl nozzle for a few minutes, it will do the same thing as running the engine & run gas.

I have a one gallon lawn mower gas tank I use while syncing the carbs and I'll run fuel through the carb & let it run for a while. I use a filter inline from the mower tank so I can keep reusing the fuel & if I run a half gallon of gas through the bowl, that ought to (I think) be the same as running fuel through the carbs "for A few minutes of run." Out of curiosity I'll check it first when filling the bowl & then again after running the fuel through it.

It seems like the main thing I need to know to adjust these floats properly is exactly what did they mean by adjusting the bike so the carbs are positioned vertically? If it means square as I thought, then the only thing I didn't do was to run fuel through the carbs for a few minutes.

More thoughts on this? I'm hesitant to proceed at this point.

 

Hmmm... I just checked my Kawasaki GPz 750 factory manual. Same carbs - BS34's. They specify that service fuel level should be checked with the bike in "a true vertical position", but I think they mean only left-to-right. The reason I think that is because they also have a picture to illustrate checking service fuel level, and the carburetors are on the bike and are clearly tipped forwards.

 

The problem is "Lost in Translation"

Vertically-Level is an Oxymoron.
Level is Horizontally.
Plumb is Vertically.

When you position the Carbs for a Float Test, ... the Carbs should be:
Level on the Horizontal Axis.
Plumb on the Vertical Axis.

This places the Center Stanchion housing the Main Jet and Emulsion Tube, in the position where the Fluid Level in the Float Bowl will be at its Maximum Fluid Capacity and not skew the Level in the Sight Tupe during the Clear Tube Height Test.

 

Rick, so the photograph above where I have the bubble centered in the bull's eye after balancing/leveling the carb bodies, does this to you indicate the proper positioning of these carbs for float balancing?

When the carbs are resting in the manifolds they are tilted forward exactly 5 degrees off plumb... Do you agree that when they say in the manual: "Adjust the motorcycle position by placing a suitable stand or a garage jack under the engine so that the carburetor is positioned vertically", that it means in case to tilt the engine 5 degrees back so the carbs are vertical?

Also, what about running the engine a few minutes before measuring the fluid levels... Do you think my running gas through the carbs as I mentioned in my immediate post above, before adjusting, would have the same effect as running the engine if I were doing this with the carbs in place?

Thanks

 

Cut to the chase.
Fill the Bowls until the Liquid used for testing overflows the Hose connedted to the Fuel Gallery.

Use the Clear Tube Method to detect the Level within each Bowl.
Determine which are Good and which need adjustment.
With an appropriate Tool; measure the Height of the Float Material above the Base of the Carb Body.

Set the errant Heights to the correct Height using the Tool and re-test all Float Heights Dry and Wet.

Keeping the Carbs both Level and Plumb during all the Testing.