Z900A4 float levels

[sprint]

What are the correct float level settings for a 1976 UK Z900A4 and where is it measured from?

I know you are supposed to a manometer but I need some initial float level settings.

Thanks

[Ultim8pc]

26mm from the base of the carb body. then when re-assembled fill with fuel and check actual fuel levels. (As correct float height doesn't always equate to correct fuel levels).

[sprint]

Thanks for the reply.

I need some further help/advise on this.

I have had the bike for some years and it has always run rich, but generally rideable. I have stripped and cleaned the carbs several times.

However, a few weeks ago it became very bad ridding it with popping and backfiring on No 3. On taking the plug out it was terribly black and sooty and all the others were running rich. So carbs off again and I have sent the enrichment plungers off to have new seals fitted.

I have again cleaned all the jets and used carb cleaner followed by compressed air to clean and ensure all the orifices' are clear.

Looking to re-build the carbs and need to set/check the float levels, hence my enquiry which I have been advise should be 26mm from body face.

With reference to the attached mine are currently around 29mm from the face of the gasket, so around 29.5/30.0mm. So logically at that setting the petrol level will be lower than if it is set to 26mm which should be causing a weak mixture and not the rich mixture that I am getting.

So is 26mm the correct setting for the std 26mm carbs or do I have another issue as if I set it to 26mm I am surely going to have an even richer mixture?

[warren3200gt]

Have you checked the voltage to the coils? Low voltage will soot up plugs pretty quickly. As all four are the same all four carbs would need to have the same issue. If it were electical both coils and all four plugs would present the same symptoms.
If your only getting 10 - 11volts at the coil that would be enough yo soot the plugs.
Maybe time to fit a wired George relay mod to power the coils direct from the battery.

coil_diagram.jpg (23.72 KiB) Viewed 18813 times

[sprint]

Thanks for the reply.

I did the 'George' relay mod some time ago, which initially seemed to help, but rich and sooty plugs remain.

However, at this stage I need some advice on the float levels as per my post and photo.

[warren3200gt]

Seems little point in setting them upside down to a measurement to me as each float will behave differently under normal use and will need adjusting using the wet method anyway. The only thing worth doing in my mind at this stage is to ensure the floats are straight and leveled with its partner. Check all the brass hinges are straight and free and that the arms are not bent or twisted at all.
Regarding resetting the tangs I go for the tang to be bent towards the valve by the width of the tang metal. Ie if viewed level there would be no gap between the bottom of the tang thickness and the top of the float arm thickness.
This tends to mean that only a minute adjustment is required when setting them wet.

[Ultim8pc]

Thanks for the reply.
I did the 'George' relay mod some time ago, which initially seemed to help, but rich and sooty plugs remain.
However, at this stage I need some advice on the float levels as per my post and photo.

Sooty plugs can also be a sign that your choke plungers seals have failed - letting fuel in when they shouldn't.

[Al]

What condition are the float valves and seats in? If they were replaced,. were they good quality ones and are the spring plungers of the 'pins' in the valve still strong? Does it have the washer / gasket / shim underneath the valve seats and are they the correct thickness?

AL

[sprint]

What condition are the float valves and seats in? If they were replaced,. were they good quality ones and are the spring plungers of the 'pins' in the valve still strong? Does it have the washer / gasket / shim underneath the valve seats and are they the correct thickness?

AL

All the seats and valves are in good condition and yes there is a very thin aluminium washer under the seats. The valve springs are also in good condition.

Is it confirmed that for the 76 A4 the static float height is 26mm from the body face, without gasket?

[sprint]

Thanks for the reply.
I did the 'George' relay mod some time ago, which initially seemed to help, but rich and sooty plugs remain.
However, at this stage I need some advice on the float levels as per my post and photo.

Sooty plugs can also be a sign that your choke plungers seals have failed - letting fuel in when they shouldn't.

As advised in post I have sent the plungers to Rob for new seals and hope that will have an impact on reducing the rich running, but I am also trying to understand why my static float heights are around 29/30mm when I have been advise they should be 26mm. At that height the petrol level with be low and should be causing a weak mixture?

[zed1015]

As advised in post I have sent the plungers to Rob for new seals and hope that will have an impact on reducing the rich running, but I am also trying to understand why my static float heights are around 29/30mm when I have been advise they should be 26mm. At that height the petrol level with be low and should be causing a weak mixture?

The low float heights probably indicate the previous owners attempt at solving the rich running..
They need to be put back to 25mm +/- 1mm which is correct for the A4.
The new Viton plunger seals will improve matters if not cure it entirely and future proof them.
You should also look at the 'O' rings on the emulsion tubes if fitted as they are a likely suspect too if original..

On another note are you sure the sooting is fuel and not oil.
Has the bike had new stem seals etc.

[bulldogbobby]

My A4 also coughs and splutters a bit at tick over and lower revs (plugs seem to indicate a little 'rich' on cylinders 1-3 and 'lean' on number 4) and I'm hoping that new choke plunger seals will improve things but am also looking at the float levels whilst I've got the carbs on the bench (Rob is changing the seals and has said to check that the pilot jet isn't blocked on number 4)
I've sourced a couple of M6 x 0.75 barbed elbow fittings for the drain screw threads and have started on number 4 as that seemed to be the odd one out - according to the manual I've got, the measurement is supposed to be 3mm (+/- 1mm) from the flange face where the float bowl and carb body meet to the top of the fuel level in the tube?

No such thing as a stupid question so here goes......
I understand that it's important to get all the levels 'right' but considering how 'fine' the tolerance is, I'm struggling to get an accurate/consistent measurement - it looks to be around 4mm to me but I seem to get a different measurement every time I look at it! Does this look ok before I carry on with the others or is there an easier way to get the measurement spot on?
Also, is it simply a case of unscrewing the pilot jet on number 4 and (carefully) using one of the tiny, soft bristle 'carb cleaning' brushes to check for blockages?
NB - The bike has electronic ignition and has stood for a number of years with very little use before I got it - although I don't think the carbs have been ultrasonically cleaned in the past, they have been off and have been 'air cleaned' before I got the bike

Cheers in advance

[zed1015]

Also, is it simply a case of unscrewing the pilot jet on number 4 and (carefully) using one of the tiny, soft bristle 'carb cleaning' brushes to check for blockages?

Unscrew it and hold it up to the light to see if it's blocked.
A brush won't get in there however small and it will need poking clear with a wire strand or jet cleaner if the airline doesn't clear it.
While the jet is out get the airline in the hole where the jet goes and feel for air coming out of the small orifice in the venturi floor with your finger tip to confirm that isn't blocked too.
Spraying carb cleaner up the hole to check it's clear will work too but may not shift any dirt like compressed air will.

[bulldogbobby]

Also, is it simply a case of unscrewing the pilot jet on number 4 and (carefully) using one of the tiny, soft bristle 'carb cleaning' brushes to check for blockages?

Unscrew it and hold it up to the light to see if it's blocked.
A brush won't get in there however small and it will need poking clear with a wire strand or jet cleaner if the airline doesn't clear it.
While the jet is out get the airline in the hole where the jet goes and feel for air coming out in the small orifice in the venturi floor with your finger tip to confirm that isn't blocked too.
Spraying carb cleaner up the hole to check it's clear will work too but may not shift any dirt like compressed air will.

Nice one - thanks mate

[sprint]

As advised in post I have sent the plungers to Rob for new seals and hope that will have an impact on reducing the rich running, but I am also trying to understand why my static float heights are around 29/30mm when I have been advise they should be 26mm. At that height the petrol level with be low and should be causing a weak mixture?

The low float heights probably indicate the previous owners attempt at solving the rich running..
They need to be put back to 25mm +/- 1mm which is correct for the A4.
The new Viton plunger seals will improve matters if not cure it entirely and future proof them.
You should also look at the 'O' rings on the emulsion tubes if fitted as they are a likely suspect too if original..

On another note are you sure the sooting is fuel and not oil.
Has the bike had new stem seals etc.

Thanks for the reply.

Look forward to fitting the plungers with the new seals.

Will set the levels to around 26mm.

Whilst the carbs are off I can do a wet level, which is much easier than on the bike, but it is such a tedious job and as another member has found very inconsistent. You do it once and think you have done it try it again and the level has moved which is why I would like to set to an initial static level but trying to understand why they are at around 29/30mm which would give a fairly low fuel level but I still have soot/rich reading plugs.

No they are not oily as I did do the valve stem seals when I did the engine.