Z900A4 float levels

[zed1015]

Don't believe that there is any problems with worn guide seal or any broken rings as the plug is dry and sooty that wipes off with your finger and all the rest or your list have now all been tested and no issue found.

Just because the plug isn't oily doesn't mean the sooting isn't from oil burning.

[Al]

This is the pic you posted in the thread; Black Plugs.
Were they in correct order left 1.......2......3.....4 Right??

You could;............put the B8 back in, weaken the mixture screw on number 3 only, drop the needle by one groove on number 3 only, remove the air filter and take it for a run.
Look at the plugs when you come back and that should help you decide if you have an oil control problem.
What exhaust? four pipes or four into one? If its four pipes is one more oily or sooty than the others at the end? Number 3 perhaps.
What condition are the coils and leads in. Did you swop them over and see what happened?
Have you measured the internal resistance of the coils? Have you measured the total resistance of; plug in cap with lead attached to coil and down to the plug on the other end to see if there is a difference between one coil / lead/ plug setup and the other combination?
AL

[sprint]

Thanks for the replies.

Whilst I accept it may be oil fouling my gut feeling is that it is not as a result of oil fouling. There is no smoke on any of the pots and the bike has been on the road since I did the engine some years ago, this a fairly recent problem.

Photo of plugs was before I removed the carbs, cleaned them replaced the seat/valves, had the choke plunges done etc, only No 3 now remains black and sooty.

Bike has original set of 4 x 4 pipes.

Plug leads and caps of No's 2 & 3 were swopped, No 3 remained black and sooty, so not lead or pug cap and I would also say coil, and I have tried new B8ES and B7ES plugs with them both remaining black and sooty.

Plug cap resistance already reported as No's 1, 2 & 4 4K8 and No 3 5K4 and this did not cause No 2 to be black and sooty when swopped.

Not sure I fully follow your advice about weakening the mixture to establish if it is an oil fouling problem?

Air screw on No 3 has already been taken out to 2 1/2 turns with no effect. When I did the colourtune the flame colour changed from yellow at 1 1/4 to blue at 1 1/2 turns so I believe the air jet and passageway to be clear else I would not see the change in the flame colour?

Can drop the No 3 needle by one groove and take air filter out, but what would I be looking at or see that would indicate/show if it is an oil fouling problem, can you kindly expand.

Everything at the moment seems to point specifically to No 3 carb as there remains the issue of why whatever I set the float level to it remains high, so apart from doing the weakening test you suggest trying another No 3 carb is going to be simplest way to eliminate it, though physically changing it is certainly not simple!

[sprint]

If anybody reading this post has a No 3 VM26SS carb body, with side air screw not underneath, or complete carb hopefully known to be OK has one that they can sell me or loan to test, all postal charges paid, can you kindly let me know.

[warren3200gt]

I think my route now would be to buy a complete bank of carbs from wherever. Then take whatever is needed and test again.
No change, just sell em on. Resolves it, you have plenty of spares or part out what you don't need to recover majority of outlay.
Bit drastic but given the money you've already spent with no resolution it may be a eventual time saving and nearly no cost solution?.

[zed1015]

There is little to zero chance of anything being structurally wrong with the carb body unless something like the emulsion tube has been overtightened and caused a fracture in the casting allowing fuel to seep through.

There are three fuel paths in these carbs and if the jetting and needle heights etc are correct there are only a limited amount of issues that will cause the problem if it is over fueling.

Choke = plunger seals ( fixed ).
Pilot circuit = loose pilot jet or blocked/partially blocked pilot air passage.
Main jet = loose emulsion tube , loose main jet or damaged /perished 'O' ring if fitted.

You should look closely at all these areas and even though the plungers have new seals there may be something stopping #3 from fully closing .

If you want someone else to inspect that carb for faults and ensure all passages are clear you are welcome to send it over and i'll look at it FOC..

[Ultim8pc]

Ideally body and slide are kept paired but needs must.

So long as the slide moves freely and doesn't have any chatter, then it's not essential.

[Al]

Photo of plugs was before I removed the carbs, cleaned them replaced the seat/valves, had the choke plunges done etc, only No 3 now remains black and sooty.

Another photo of the 'now' situation would allow a better assessment of the many changes that have happened since that photo was taken. In the picture; number 3 does not look too bad ~ rich, but on the safe side of correct!

Plug cap resistance already reported as No's 1, 2 & 4 4K8 and No 3 5K4 and this did not cause No 2 to be black and sooty when swopped.

I couldn't understand what 4K8 etc means, is that 4,800?

Air screw on No 3 has already been taken out to 2 1/2 turns with no effect. When I did the colourtune the flame colour changed from yellow at 1 1/4 to blue at 1 1/2 turns so I believe the air jet and passageway to be clear else I would not see the change in the flame colour?

This means; no effect on overall colour of plugs after a run?
If you can adjust the flame colour from full yellow to full blue in 1/4 of a turn it suggests that the fuel level / pilot screw relationship is working reasonably well within the prescribed parameters and that those two criteria are not the primary cause of an 'over-rich mixture through the rest of the range!

Can drop the No 3 needle by one groove and take air filter out, but what would I be looking at or see that would indicate/show if it is an oil fouling problem, can you kindly expand.

If its oil, you cant remove it from the equation. If its excess fuel you can artificially weaken the entire landscape by removing the air filter temporarily. If its oil it will still show up that way. If its excess fuel it will all go weak. If its both, you will get something entirely different looking!

If you can do another picture; try to resist the temptation to rub the soot / oil with a finger to see what it is. There are some critical indicators for heat range, mixture and ignition timing which rely on being able to see where the deposits are and where they stop / taper out!
Dropping the needle by one groove or half a groove on number 3, if you have those 'half' shims was a 'might as well do this at the same time' test. It might highlight a worn needle jet or jet needle or a jet needle that sticks in the jet with restricted movement.
You would need the B8 plug back in number 3, because the temp. increase with no air filter would give a misleading indication of the state of 'cleaning' of the plugs!

AL

[sprint]

I think my route now would be to buy a complete bank of carbs from wherever. Then take whatever is needed and test again.
No change, just sell em on. Resolves it, you have plenty of spares or part out what you don't need to recover majority of outlay.
Bit drastic but given the money you've already spent with no resolution it may be a eventual time saving and nearly no cost solution?.

That is not a route I really want to go, replacing at least 3 carbs that are seemingly OK. Have already spent over £200 with no real progress so far is frustrating. Floats arrived today.

If it is down to the No 3 carb alone then there must be some physical reasons why, which at this time is not obvious, so if a No 3 body/carb was available it would help fairly quickly to eliminate or not if it is the carb?

[sprint]

There is little to zero chance of anything being structurally wrong with the carb body unless something like the emulsion tube has been overtightened and caused a fracture in the casting allowing fuel to seep through.

There are three fuel paths in these carbs and if the jetting and needle heights etc are correct there are only a limited amount of issues that will cause the problem if it is over fueling.

Choke = plunger seals ( fixed ).
Pilot circuit = loose pilot jet or blocked/partially blocked pilot air passage.
Main jet = loose emulsion tube , loose main jet or damaged /perished 'O' ring if fitted.

You should look closely at all these areas and even though the plungers have new seals there may be something stopping #3 from fully closing .

If you want someone else to inspect that carb for faults and ensure all passages are clear you are welcome to send it over and i'll look at it FOC..

Thanks for replies and suggestions. Want to do as much as I can before embarking on removing the carbs again. However, that is looking to be increasingly likely so if I am not able to identify anything amiss with the carb I would gratefully take up your offer to inspect it, thanks. Will let you know if/when I can do that.

[sprint]

Ideally body and slide are kept paired but needs must.

So long as the slide moves freely and doesn't have any chatter, then it's not essential.

Thanks, assuming I am actually able to find a No 3 body/carb?

[sprint]

Photo of plugs was before I removed the carbs, cleaned them replaced the seat/valves, had the choke plunges done etc, only No 3 now remains black and sooty.

Another photo of the 'now' situation would allow a better assessment of the many changes that have happened since that photo was taken. In the picture; number 3 does not look too bad ~ rich, but on the safe side of correct!

Last photo, No1 on left to No 4 on right. Unfortunately I have wiped most of the carbon off No 3. The others have what I consider OK brown centers with the usual black threaded outer circumference as bike was on tick over for a while.

Plug cap resistance already reported as No's 1, 2 & 4 4K8 and No 3 5K4 and this did not cause No 2 to be black and sooty when swopped.

I couldn't understand what 4K8 etc means, is that 4,800?

Sorry, yes mean 4800 and 5400 ohms resistance.

Air screw on No 3 has already been taken out to 2 1/2 turns with no effect. When I did the colourtune the flame colour changed from yellow at 1 1/4 to blue at 1 1/2 turns so I believe the air jet and passageway to be clear else I would not see the change in the flame colour?

This means; no effect on overall colour of plugs after a run?
If you can adjust the flame colour from full yellow to full blue in 1/4 of a turn it suggests that the fuel level / pilot screw relationship is working reasonably well within the prescribed parameters and that those two criteria are not the primary cause of an 'over-rich mixture through the rest of the range!

That is my conclusion, but will do another colourtune to check that remains the same?

Can drop the No 3 needle by one groove and take air filter out, but what would I be looking at or see that would indicate/show if it is an oil fouling problem, can you kindly expand.

If its oil, you cant remove it from the equation. If its excess fuel you can artificially weaken the entire landscape by removing the air filter temporarily. If its oil it will still show up that way. If its excess fuel it will all go weak. If its both, you will get something entirely different looking!

OK, will try this. Can I drop the needle without having to remove the carbs? I assume that I am going to have to remove the lifting rod to get the slide out, but can that be done in situ?

If you can do another picture; try to resist the temptation to rub the soot / oil with a finger to see what it is. There are some critical indicators for heat range, mixture and ignition timing which rely on being able to see where the deposits are and where they stop / taper out!
Dropping the needle by one groove or half a groove on number 3, if you have those 'half' shims was a 'might as well do this at the same time' test. It might highlight a worn needle jet or jet needle or a jet needle that sticks in the jet with restricted movement.
You would need the B8 plug back in number 3, because the temp. increase with no air filter would give a misleading indication of the state of 'cleaning' of the plugs!

Will have to do another photo of the No 3 at some time without touching it. Can you explain what you mean by 'half' shims as I am not familiar with that or as to if they apply to my bike/carbs?

AL

[Al]

Good effort but no cigar Really need to see all four and not on tickover, sorry but i am determined to win the £500 for finding the answer.
The 'half' shims were on my CV's and again now on the radial flatslides. Dont know where to get them and you may not have them but they are full circle like washers, and half the thickness of the space between two clip grooves on the jet needle. ie. they give a half a groove of fine tuning.
I am sure you can just lift the needles out without having to remove the carbs but not having dont it i cant say for sure.
It does look superficially as though the number three is richer than the others but well within the range of adjustment provided,... for a set of 40+ years old, worn carbs.
If you end up with slightly different settings for all four carbs then so be it. That is what is needed if circumstances dictate. My ten year old flatslides are all different for a range of reasons, circumstances and attributes. They also fluctuate according to temp, humidity, fuel used, condition of the other components in the chain.
If you rebuilt the motor a few years back, what might the reason be for the 100PSI compression pressures which is low by any standard? 100PSI is 6.8 to 1 in a world where most things seem to run at 10:1 or above and modern lean burn engines (designed to run the fuel which is supplied) will be twice the combustion chamber temperatures you have got!

Just in case it comes up later; do you have a set of waterproof trousers which you keep under the seat which have been sucked into the air intake?
AL

[sprint]

The VM26SS cards, I believe, do not have the half shims that you refer to.

Will look to drop the needle by one grove over the week end and remove the air filter and do another plug chop at around 60mph, but remember to take my camera with me.

The problem with the No 3 is that with the amount of carbon build up that was being experienced there is a completed breakdown of the plug firing and as a result it was missing and backfiring, which eluded me to the problem.

I am not bothered about all the carbs having the same settings only that they allow the bike to run.

It did not have particularly high compression after the re-build. 100 psi is the min limit, according to the manual, and I am happy with that, the important thing is that they are all more or less bang on that and as a 47 year old bike on it's original bore acceptable to me.

There still remains the mystery of why the flat level remains high whatever position the tang is set to, which must be having an influence.
I will try one of the new floats, but can't see that having any effect?

No I do not have anything that has sucked into the into the air intake. On the A4's it has the addition of the snorkel to get through, but all is clear.

[warren3200gt]

Andy, when you did the engine rebuild is there any chance you might have accidentally fitted the oil ring expander with the ends overlapped restricting the oil scraper rings from being able to expand to the bore size? It wouldnt affect compression but would definately cause a black plug.
It doesn't explain the inconsistent fuel bowl level of course but I'm not sure a couple of mm's high fuel level would cause the plug to be a sooted to the extent it showed in your picture. Just thinking aloud really!