Carburetors

[DonB]

Hi, z9 A4, carburetors continuously weeping out of the overflows on the float bowls.
Any ideas for diagnostics would be very helpful please.

Cheers

[DavidZ1R]

Either float levels to high, muck on one or more valves making them stay just open a touch, one float sticking not switching off the fuel, or if it's on the side stand fuel drifting to the lowest carb, 1 and 3 and dribbling out, check which overflow pipe or pipes it comes out of.

[Pigford]

If it's via the little brass tube at bottom of float bowl - could even be the brass tube itself has split, inside the float bowl - not unknown!?

[Garry.L]

Also if it's happening when the bikes been stood it's worth checking the Fuel tap itself isn't passing. Pretty common on these old gravity taps - more so if they've dried out at some point.

[DonB]

Thank you will try your suggestions

[needaz1100r]

Also if it's happening when the bikes been stood it's worth checking the Fuel tap itself isn't passing. Pretty common on these old gravity taps - more so if they've dried out at some point.

That's definitely an issue, the carbs still shouldn't over flow though, unless it's a rotted diaphragm and fuel is getting town the vacuum pipe.

[Ultim8pc]

A combination of any of the following:
Incorrect fuel level
worn or sticking float valve
Leaking fuel tap
Perished float bowl gaskets

You need to get the carbs out and get the bowls off and check for correct float/fuel height, gasket and float valve condition and deal with accordingly.

Get in touch if you get stuck or need help.

[johny brando]

Hi, z9 A4, carburetors continuously weeping out of the overflows on the float bowls.
Any ideas for diagnostics would be very helpful please.

Cheers

Most probable it is the Float valves not shutting off properly - either the fuel HEIGHT is incorrect & too high within the float bowl, probably a Dirty or worn Float valve assembly, so they are not seating 100%- or a floats or floats that are pin holed & taking petrol on board ( shake & listen /feel if you can hear or feel fuel fuel within to test them for leaking.... quickly immerse each float in boing hot water & look for bubbles existing ..that shows the leak point... so then if required you can repair with soft solder )- or maybe it's a float or floats are dragging or catching some where due to probable distortion in some way this stopping full pressure on the float needle from being able to fully seat & seal- Or perhaps float pins are perhaps distorted or damaged causing drag on their floatation . Best fully clean & inspect all & then try again .....= Still the same...well now using a steel rule or Vernier gauge set each float height at 24mm ....give or take 1mm and then it's best to set the FUEL LEVEL in each carb .... this is favourite by far !!! ( the reason for this is ...the Fuel level is what your chasing & the float height whilst likely it is close........it is not always truely representative of what is happening with in the float chamber & thats whats more important !!!! )
To do this you need to make up your our own fuel level gauge kit = it's easy use the existing float bowl drain point screw or bolt hole & if thats is bigger than 6 or 8mm threads then you need to just drill and tap a 6 or 8mm threaded hole in it , this is from just one carb alone ! ( you don't need 4 of them ! ) so now 'maybe' you have had to drill & tap say a 6 or 8mm threaded hole in the existing float drain bolt head , now you need a similar 6 or 8mm threaded bolt or screw . Then with what ever size thread you have choosen to use.... drill small hole right through it's entire length & then cut the head of it. Then carefully grind the threat off about 1cm at one end.... this is to take the clear plastic tube that you will be looking at when setting the fuel levels....then at the other end with PTFE tape wrap the thread a few times so it seals & screw it into your float chamber bowl drain point that you may have had to prior drill & tap & then hold the plastic tube up against the bowl & carb body interface , turn fuel and note where the fuel level settles = ( a visual of this is shown in Kawa manual ) Then set your fuel levels at 4mm down from the lower edge of the main Carb body / Float body mating interface ( to do that carefully bend the tang between the floats to alter the shut off height within the chamber ..this may take couple of adjustments to get it correct). You should check & then adjust again until you get it dead right ....then hold each individual carb on test with the fuel LEFT ON and with the bike standing in a level plain on both axis .....Hold each test carb like this for 15-30 mins ...and if the fuel level remains static = Alls good ' & move on but & if the fuel level creeps up ....then thats the carb... or 1 of them thats giving you issues, so then ( swap internals from another known good carb in the bank ....to find the culprit & source ) then move onto the next carb & so on .
Sorry this was a bit long winded I know...but you try explaining it better without say READ THE bloody MANUAL !!!!!!!! Hope this is of some assistance. Johny B.

[Ultim8pc]

Got to agree with Johny, the actual fuel height is critical and often doesn't directly correlate to the float height.
I set the float height and then measure the factual fuel height also - as you can find the actual fuel height isn't within the correct parameters although the float height is.