Z900A4 float levels

[zed1015]

That 3rd plug looks like burnt oil fouling.

[warren3200gt]

Rob, how much does the fuel level really affect plug colour. Couple mm enough to really soot a plug to the point of failing?

[zed1015]

Rob, how much does the fuel level really affect plug colour. Couple mm enough to really soot a plug to the point of failing?

No!
A very rich pilot mix will foul a plug but only if on tickover or stuck in slow moving traffic a while.
Once moving it's enough to burn it off.

[warren3200gt]

That's what I thought. To me it looks like Andy has a bigger issue than the no 3 carb fuel level causing the issue.

That no3 carb inconsistent fuel level is intriguing though.

[zed1015]

That's what I thought. To me it looks like Andy has a bigger issue than the no 3 carb fuel level causing the issue.

That no3 carb inconsistent fuel level is intriguing though.

Reading back through the thread i think the actual fouling to plug failure isn't the issue now but just some hesitancy at low rpms and the sooty plug.
This would point to low rpm fouling that burns off.
Either overfueling/flooding at idle, inlet valve stem seal or possibly a ring issue.
I'd say that the improved colour on the other plugs is due to the new plunger seals and the fouling on 3 was due to a stack up of leaky seal and this other issue which now isolated is only enough to soot the plug.

[sprint]

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!

Not sure that follow what you are asking? The ends of the expanders as far as I know would have butt jointed, but without taking apart one can't know but I am sure there would have been other issues long before now as the No 3 sooting has only developed this year and the engine was done several years ago. I'm not sure if you could physically overlap the ends and be able to get the barrels on, but again I would have thought there would have been some fairly immanent issues following the original re-build?

[warren3200gt]

Ah sorry, I thought you had recently rebuilt the engine and the issue with no 3 carb / plug had appeared as a result.

As Rob pointed out maybe the high fuel level is misleading and its a mechanical issue that's causing the black plug. Have you taken the header pipe off no 3 cylinder to see if there's any oily residue in the port? That would maybe rule in / out oil fouling and suspect valve oil seal.

[zed1015]

Have you taken the header pipe off no 3 cylinder to see if there's any oily residue in the port? That would maybe rule in / out oil fouling and suspect valve oil seal.

It's more likely to be an inlet guide seal leaking slightly to affect the plug constantly while running which wouldn't show up as an oily exhaust port as that small amount would be burnt up in combustion.
A leaking exhaust one will just wet and carbon up the valve stem and blow oil down the pipe but not enter the cylinder while running.
If the problem was wet fouling on start up then this could be either inlet or exhaust.

[warren3200gt]

Good point we'll made Rob!

[sprint]

I'm still hoping it is a carb issue as anything else will be a pain in the butt.

Transferred all the jets, seat, valve, float pivot pin and float from No 4 to No 3 and all of No's 3 to No 4. However, I also fitted a new float to No 4 which went it without any tang adjustment.

Did another plug chop at 60 mph, see gloved photo. 1st time the insulator of No 3 has had a slightly normal colour.

On return home killed engine and did not let it idle.

Checked float levels on all carbs and they have all remained at correct levels.

Removed plugs, see attached. No 3 still very sooty but again insulator is not totally sooty as previously.

No 3 air screw currently 2 turns out.

Bike rides down to 25 mph and will pick up from there fairly smoothly.

Will try dropping the No 3 needle by one groove and test with and without air filter when I have to time.

[Al]

first pic, gloved hand, 60MPH;
#1 A little rich but heat range and temp. perfect. Colour change is on radius of groundstrap which is where it should be.
#2 A little rich and running hot. Colour change nearing the base ring and top threads showing signs of reddening. I still think this is a weak or failing coil issue.
#3 Too rich. Maybe fault with main jet, needle jet, jet needle assembly being; worn, scored, bent, drilled out, stepped etc. Drop needle one groove and see.
#4 No idea. Is it even running? It looks like its not firing and just getting washed by fuel!! That said, it was showing signs of oiling in previous photos and again to an extent in this one. It looks 'wet' inside!

Second pic, home again, no idle;
#1 Still looks a little rich
#2 Still looks a little rich and a little hot but not so obvious from this side.
#3 Still too rich and one needle groove, clip movement may fix that.
#4 Looking a little blotchy but better than at 60 MPH. Still could be taken to be oily but so hard to see from just a picture.

Speaking for myself i would address the 'number three' running rich situation first to get them all the same. If you run it without the air filter keep an eye and ear on number 2 so as to not let it get too hot and cause any problems for you there.
AL

[sprint]

Plugs of No 3 and No 4 were swapped as I do not have the ability to thoroughly clean plugs, nor a new supply to keep changing every time I do a test.

So I cleaned No 3 as best I could and put it into No 4 and moved No 4 to No 3, which is why it probably looks so bad, all pots were firing OK.

Have dropped the needle on No 3 but constant rain here means that it may be a while before I get out to test it again. Will run it with air filter and check No 3 before removing the air filter, but you need to do a bit of a ride before the plug condition changes, but may limit to 50 mph?

[Al]

but may limit to 50 mph?

Keep the continuity and do it at 60MPH.
Took this pic at Donnington yesterday. Its a bit rich, but a situation that was forced on me by a failed Dyna 2000 module. The timing of the two modules is very different.
What you can see is, it has the 'Colour' on the base ring which is more than half way round meaning more than 50% of the base ring shows the mixture. The remaining part (in sooty black) is the area that the ground strap is welded to and where it runs colder and looses its heat from,.. to the head. The colour change is just past the radius of the ground strap (the change from brown to black). That is an indication of the 'heat range of the plug' (temp. of the combustion chamber) and in this case its a different plug from the standard quoted. Its a colder running plug.
This has no specific relevance to youre situation as such except to say that youre number 1 plug (home again, no idle) exhibits similar attributes and looks to me to be the aiming point if you needed a guide for where to head to.
You should be able to click on the picture to zoom it up!
AL

[sprint]

Thanks for info about the plug taken at Donnington.

I have been away with some friends on bikes for the last few days and now back, so subject to the weather I need to get out and try the bike now that I have dropped the needle by one groove on the No 3 carb to see what impact, if any it has?

Will repeat tests at 60mph, as suggested, to maintain continuity.

[sprint]

Took the bike out again today on which the No 3 carb has had the needle dropped by one groove.

Air screw on No 3 set two turns out to weaken the mixture even though it colourtuned around 1 1/2 turns out.

Plugs are No 1 to right to No 4 on left.

1st photo done with 60mph chop and is with air filter fitted.

2nd photo done with 60mph chop and air filter removed.

3rd photo is done on returning home with air filter fitted and no tickover.

I am not looking for ultimate performance and perfect running, I have modern bikes for that, I just want to use it for pottering around the back lanes between 50 and 60 mph.

If No 3 needs the needle dropped by one groove it does not bother me as long as it runs OK and is not going to cause the backfiring and missing it previously had.