TOPIC:

Hi,

I have problems trying to set carb float height using the clear tube method.

The carbs had been leaking at the bowl gaskets and needed a good clean. I completely stripped and rebuilt them using an ultrasonic cleaner.
After assembly I tried to set the fuel heights.
The carbs are off the bike so it should be easy to do.

Whatever I try I cannot get it right.
If I set the tabs right to get the fuel at 3mm below the carb flange it is so high no fuel comes into the carb.
The best I can get the level is at the bottom of the carb body, not below it.
I am also seeing inconsistencies where it seems nearly right then I measure again and it is different or even goes over the top of the float bowl.
The float valves look good with no signs of wear. They were replaced about 10 years ago but the bike has not been used that much since.
I have also tried to ensure the float tang is as level as possible thinking an angle that is too high might not work well.

Is it possible for the buoyancy of the floats to change with age ?

I am technically competent and have tried to get this right for many hours.
Please give me some advice and help me to retain some sanity

Thanks,

Jim

Could it be you have install the carb floats upside down after your carb rebuild???

Chances are the float needle valve is after market and not genuine, which kinda means all bets are off. Genuine floats valves generally need the float tang to be just above the float hinge by about the thickness of the metal. However aftermarket float valves could be a different length or the spring strength in the actual valve could be weaker or stronger or it could be a combination of both.
All you can do is set the tang to achieve the correct fuel height regardless of how high or low it is. Only downside is that if the tang is too far off horizontal with the float hinge the float valve needle may not slide up and down correctly due to angle which will result in allowing fuel to flow into the bowl continuously and not do its job of shutting fuel flow when the bowl is full.


As Scirrocco says, floats in upside down would also allow continuous flow.


PS welcome along Jim, where in the UK are you? Im also a UK member living just by Brands Hatch.

The points on the float valves already mentioned are well worth inspecting. Also, there are several different models of the float valves. What carbs are you working on? For my Z1's they have a 2.0 scribed on them.

It's very difficult to put the floats in backwards because of the stopper tang.

Hi Warren3200gt and thanks for the welcome.
I live in Sandy up the A1. I know Brands very well due to club racing and track days. Must have done over a 1000 laps round there.
The float valves came from ZPower but can't remember if they were genuine or not.
ZPower sell both so I assume I would have gone for the cheaper option
I will phone ZPower for their advice

HardRockMiner, the points on the valves are ll good with no signs of wear.
The bike is a Z1000 A1. I cannot find any identifying numbers on the carbs but they look identical to original as seen in manuals

If original, the carbs would be VM26SS with fuel/air screws.

The float valves have a number that's visible when they are installed. I'm not positive but I think they should be 2.0. When adjusting the floats you need to make sure the metal frame is flat. I always check my floats with the carbs upside down. When a float is closed the measurement from the edge of the bowl to the edge of the rubber float should be approx 16 mm. I always check this before assembling and it usually results in being very close to the 3.5 mm using a clear tube. That saves a lot of assembly/disassembly work. I always work with one or two carbs at a time, usually with them out of the frame. I find it's easier to work with them that way. The two carb method is what I use for Z1 carbs because of the adjusting mechanism on them.

Note that the tangs cannot be bent too much or the float needles will stick and not close. Be careful when installing the bowl gasket...sometimes a float can catch on it, particularly if the float has been bent a bit. I sometimes shave the inside of the gasket to make sure it doesn't touch the float.

Jimwarrenuk wrote: Hi,
If I set the tabs right to get the fuel at 3mm below the carb flange it is so high no fuel comes into the carb.

I don't understand this part. You are using the clear tube method right? If so, you are measuring fuel level, so please explain this part "...no fuel comes into the carb."

Had the same problem with one of my floats. There is a fine line between getting the float to work without bending the tang too much. Bending the float arms to get it close with the tang level then bending the tang just enough to make the valve close fully in the right place worked. At some point in between the valve wouldn't open at all so it is a very delicate adjustment. If there's question if the float has lost it's buoyancy, you can place them all in a pan of water to compare them to each other. Brass floats are notorious for this but the plastic ones are more forgiving even when damaged.
Steve

Nessism wrote:

Jimwarrenuk wrote: Hi,
If I set the tabs right to get the fuel at 3mm below the carb flange it is so high no fuel comes into the carb.

I don't understand this part. You are using the clear tube method right? If so, you are measuring fuel level, so please explain this part "...no fuel comes into the carb."

I, too, am really confused by this. How can you know that the fuel level is 3 mm below the flange if no fuel is coming into the carb? Or that it is too high?

Jimwarrenuk wrote: Is it possible for the buoyancy of the floats to change with age ?
Thanks,
Jim

Hi Jim,
I suspect, but have yet to prove, that the black plastic foam floats absorb alcohol from the ethanol degraded fuel we're forced to use here in the US.
Bill

I can't see any number on the float valves. Either on the brass bit that screws into the carb body or the silver bit that lifts to stop petrol flow.

When I say no fuel comes into the carb I mean that to try and get the fuel level down to 3mm below the carb body flange, I have to adjust the float so much that it closes the valve when I put the bowl back on so at that point no fuel can get in.

What I've tried is this …
Started by getting the main brass piece on the float looking as straight as possible.
Set the tang level with the main brass piece it is attached to.
Tested fuel level - it was too high reaching the top of the bowl.
Tried adjusting the tang to lower the level. Seemed to make very little difference.
Eventually after tweaking the tang the angle was getting quite high which is not good so tried bending the black floats down slightly so the tang could stay more level.
When doing this, the floats were lower than the bottom of the bowl so when I put the bowl on it lifted the float and closed the valve so no petrol came into the carb.

I've tried every possible setup of tang angle, float position with regard to being level with main brass plate etc on all 3 carbs and whatever I do the level comes out too high.
I have also seen inconsistencies where the level changes and goes even higher when I do not change anything.
I thought I had one right and the next time I turned on the fuel feed it was over the top of the bowl.

I'm completely out of ideas.
I've tried every combination of float tang position on all carbs.
The valves are in good condition but here is a good chance they are not genuine parts so maybe that's it.

As others have pointed out, there seems to be a fine line between finding your bike in a puddle of gas after sitting a few hours, and a dry floor. I re-jetted my Kz1000 this week, and wet checked the float levels, Also make sure the petcock is shutting off like it should.
I made up a carb holder with a piece of plywood and 2 old carb holders to hold them level for the clear tube test.



I whipped out my Johnson to make sure the carbs were level:



This method works well. I set my fuel tank on a shelf above my air compressor, maybe 1' above the float bowls. If the tank is too high, it can apply too much static fuel pressure to the float / needle assembly as remembered from fluid power and physics classes.



Once everything is hunkie dorey, the fuel levels can be checked with confidence.


* NOTE: The was the second try after I had already installed the carbs the day before, yet found the bike badly flooded the next day. I had left the petcock in the prime position, but did not trust my first attempt at checking levels. I removed them again and tweaked all 4 floats to a lower level than was previously set.