Z900A4 float levels

[sprint]

Really can't remember where I got the carb kits from, but I would have gone for what I believed to be good/reasonable quality.

Plungers are fitted just need to do a static balance and then fit them a do a vacuum balance.

Attached is photo of needle valve tang.

[Ultim8pc]

Hope you finally have this resolved.
NOTE.
There are many sellers advertising Keyster kits and actually selling cheap Chinese stuff. Keyster kits come in red and blue branded boxes.

[sprint]

Thanks

The Kester seat/valve sets you supplied are certainly well made and have certainly helped to solve my problem.

It's been an interesting few days from which I have learnt a lot and which may help others who have a similar problems?

Proof of the pudding will be no black sooty plugs and a nice smooth, jerk free and easy pick up from a closed throttle?

[warren3200gt]

Worst case it's a step forward, best case everything is sorted.
Do you have a colourtune plug to set airscrews?

[sprint]

I do have a very early colourtune which provably has not been used for around 40 yrs.

Have normally found that adjusting to give max revs and then closing a bit has usually worked but the bike has been plagued with snatching and stalling from rest of if you close the throttle and then open it again.

Hoping that this may have been as a result of the rich mixture and has been cured or improved with what I have just done?

If it persists I may dig out the colourtune and see what the flame colour is?

[warren3200gt]

So the set up is stock right through from airbox, carbs, exhaust now?
If so then stock book settings should get you 99% of the way there, then when you do a plug colour check (fingers crossed they'll not be black) will tell you what to do to get them spot on.

[Stagman]

I bolted my carbs to a piece of MDF then held the whole lot in a vice vertically/horizontally, connected my fuel supply and did all my fuel height measurements and adjustments like this. Thats as good as you can get i think.

[gray]

Me too, I've made a shaped steel plate that bolts to 2 unused bolt holes in the set of carbs ( near where the cable quadrant is, if memory serves) and allows the set to be mounted vertically in a vice and fed by a remote tank.

[Ultim8pc]

I do have a very early colourtune which provably has not been used for around 40 yrs.
Have normally found that adjusting to give max revs and then closing a bit has usually worked but the bike has been plagued with snatching and stalling from rest of if you close the throttle and then open it again.
Hoping that this may have been as a result of the rich mixture and has been cured or improved with what I have just done?
If it persists I may dig out the colourtune and see what the flame colour is?

I've used a Colortune since the early 80s. On my second one now...

[sprint]

Well did all the static and vacuum balancing. Also used the colourtune to set the air screws, all between 1 1/4 and 1 3/4 turns out.

Went for a ride, a lot better with just a light stuttering and stalling when closing and opening the throttle, particularly after coasting.

Did a plug check when I got home only to find No 3 black and sooty, see attached. All the rest had a brown core which I am happy with, but with No 3 sooty I'm back where I was a week ago, though at that time it was missing and backfiring on No 3, but I had not gone very far today so that may be the same outcome with more miles?

So I checked the wet float levels, No 1 and No 4 OK No 2 was now low but No 3 was now back at it's high level and so the most likely cause for the plug being black and sooty.

Well pissed off!

Raised the tang on No 3 so the valve barley moved, still high.

Swapped the floats and valves between No's 1 and 3, to see if it's the float yet No 3 remains high. Still got to sort out why No 2 is now low?

How on earth can they have all been OK with the carbs off, checked several times, for them to now move when fitted to the bike and after some use?

I'm at a total loss of what to do!

[warren3200gt]

At least its a step forward! First thing I would do no is readjust floats 2 & 3. Can't think of an obvious reason they would've changed, especially as they have gone in opposite directions.
Once re adjusted, next I would swop out no 3 plug for a new one and swop plug leads 2 & 3 over and see if the issue moves. Existing no 3 plug could be weak.
Also do a compression check. Cylinders 2 & 3 are normally lower than 1 & 4 due to lack of cooling. Low compression will cause poor combustion and soot up a plug.
Have read through below and see anything jumps out at you.

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[sprint]

Thanks for the reply and suggestions. I did adjust the tang on No 3 that was now reading high to the extent that the valve barley had to move before closing it and it remained high. Swapped No 3 and No 4 floats over, yet No 3 was remained high.

So the indication was that is not as a result of the float?

With No 3 seemingly remaining high with new valve and seat there is clearly something amiss which is most likely the cause for the black sooty plug.

Whilst the other suggestions are worth looking at if with a correct wet float level the plug remains sooty I've got to find a solution as to why No 3 remains high what ever I do and also find out why No 2 has now gone low.

So I really need to get the wet float levels sorted before delving into another series of tests that may not even be relevant as all the other plugs are OK and it is only No 3 with the high level that is dry black and sooty even with a new plug fitted.

I'd be happy to replace the floats, but at this stage don't have any confidence that they will make any difference but I have now got nothing else to try?

I really am lost as to what more I can actually physically do, as logically the float levels can only be down to the valves and seats, which have been change or the floats themselves, barring anything physically stopping the floats to rise or the valve to seat?

[warren3200gt]

Well if its not the floats as you've swapped em over and it's not the new needle/seat I can't think of anything other than a hairline crack in the body or fuel getting past the seat thread that's allowing fuel into the bowl bypassing the needle/seat.

Maybe remove the float and needle/seat and put a bolt in the seat thread to block it. Put the bowl back on and open fuel supply for 10mins then see if there's any fuel in no3 bowl. Or ptfe the seat thread to see if it helps?

It's an odd one!

[zed1015]

If i'm reading this correctly it's number 3 that shows signs of richness no matter what you have changed ?
If this is the case and it's definately not excess oil have you checked for leakage past the needle jet tube and are the plug readings taken after a plug chop at speed or just when the engine has been shut of at idle..

[sprint]

Been for a ride this morning, not on the Z900 and have just done another wet level test and all are now OK!!!!!!!!!!!

The only difference between when I re-tested yesterday and today is that the engine is now totally cold, so is it a temp related issue as No's 2 & 3 are on the inner and would in principle get the hottest?

In desperation I have ordered the set of Suzuki floats, but struggling to see that there is insufficient lifting force (buoyancy) in the existing float(s) to provide the necessary 1 to 2 mm required lifting force to close the valve with the tang bent upwards as it was?

The petrol will be hotter and therfore less dense when the engine is hot so perhaps in combination with potentially degrading float(s) causing the wet level(s) to change from their room temp settings? (Probably grasping at straws here?)

Have not done a plug check at speed, only at idle, which is probably OK as it pulls well at speeds over 40/50 mph, so it really seems to be at the low speed when you are mainly on the pilot circuit.

My understanding is that if you have the float level too high, particularly at low speed, more of the holes in the emulsion tube will be covered by petrol resulting in a higher fuel/air ratio and hence the rich mixture?

Clearly I need to get all the wet float levels consistent before going off and looking at other potential causes for No 3 remaining black and sooty? For as long as I keep measuring a high wet float level in No 3 one has to assume that this is the cause for the plug issue?

I've taped the floats up on both No 3 and 4 and there is no leakage and they more or less stop the flow as soon as the valve is closed and not requiring the sprung loaded plunger to to be pushed in.