New here, looking for guidance

[John Reeves]

Hi, actually been in the club a while but never got round to stuff. I have a Z900 A4 US import that was rebuilt by Dave Marsden for a classic show maybe 4/5 years ago, I got it from the fella that allegedly bought it from him the show. It's a very sound beautifully presented bike but right from the beginning I've had problems with badly oiled up plugs on cyl 1,2 & 4. Cyl 3 has always been good. I've cleaned carbs, checked they got the right jets (it didn't so I returned to standard 15's) and swapped them over between carbs, to rule out one being off. I bought a vacuum gauge, they were out and the running improved a bit after I'd balanced them. checked and adjusted float levels, they were pretty much on the button, but set them right. All this improved a little. I've now got the Air Screws at 3 turns out on Cyl 1&2, 2 turns on Cyl3 and 2.5 on Cyl4. Ok, so now it is running way, way better, but surely this isn't right? there's gotta be something more basic wrong. Apologies for the amount of info here, but i think it's all relevant. I'm near heathrow airport, does anyone know of someone with a magic wand, please ????

[warren3200gt]

A bit of info you have missed out is what exhaust does it have, I assume 4 x 4 but repop or factory? The repop ones are more restrictive than the originals.
Have you colourtuned it? as those airscrew settings sound way lean to me but that contradicts the sooted plugs. Do you have airscrew AND fuel screw or just airscrew carbs?
So, need to know what air filter and what exhausts and what carbs please.

There are a few guys in the club over your way who will undoubtedly be happy to help and will be along soonish.

[Pigford]

Sooty plugs - check 12v at coils when running.
Valve clearance must be checked too.
Whack in a new set of Denso plugs.

[John Reeves]

Hi Warren, I believe the exhaust is the Z-Power pattern (as the bike was refurbished by them).
I've tried colourtuning and those settings seem to be the best I can get.
The carbs are standard Mikuni,,,,,,,,,, OMG whilst checking this out I've spotted what might be a split in the rubber intake on cyl 3 (the lean one) how did I miss that..... FFS, I'll test spray around it, but it's coming off anyway, update later. feeling potentially v stupid but also sooo happy........

[warren3200gt]

Hi John, Obviously need to get that fixed if it is a split. Concerning the carbs, air screw on the side and fuel screw underneath or just airscrew on the side?
When colourtuning what results were you getting? I always go full blue then back off to get the merest hint of orange at about 1500 rpm. Obviously no 3, if it is split would give you a false reading.
This normally results in the airscrew being 1 1/2 to 2 turns out from closed. At 3 turns out you should be way lean which is why I said it contradicts the sooty plugs. As Pigford says also check you voltage to the coils and the other bits. Low voltage will also create issues. Correcting that can be a chore going through all the connections ensuring they are good but it usually ends up being the kill switch or the battery itself.

Definitely put Denso plugs in if they are not already. NGKs, once sooted, never seem to run right.

[John Reeves]

So it wasn't a split, the carb wasn't installed properly, the rubber was pinched inside the carb blocking the opening to the inlet a little and probably also letting in air past the clamp which wasn't seated properly. Anyway, I've ordered a new set (4) from Z-Power and will get it all back on properly....

Carbs are 26mm Mikuni (confirmed with a micrometer 2 mins ago) there's only an air-screw (as in Air inlet side of carb, there's no fuel screw, just a blanked off hole where it would have been, I think I've read they did away with the adjustment due to emissions or something.

In Oct 2017 the Air Filter was changed to a K&N by Debben who also fitted Dyna S Electronic Ignition and interestingly removed carbs to increase the pilot and main jets, I since put the standard jets back in BUT crucially, looking at their invoice, they removed the carbs, which ties up precisely with when the sooting plugs issue first arose, i guess they didn't put them back properly as I've not had them off, fingers crossed it's main issue.

Battery was replaced spring 2018 and is kept on an Optimate battery conditioner due to irregular use.

I'm not great with electrics, so will have to look at how to check the coils voltage, once I've got it back together, and re-balanced with the vacuum gauge and colour tune, which hopefully will give better results with the carbs installed properly.

Denso Plugs: which ones please ???? Feeling happy coz we've found a problem...

Thanks to Warren and Pigford.

[warren3200gt]

Good you found an obvious issue re the carb inlet boot. Easily ticked off the check list.

Carbs being airscrew simplfies set up so also good.

Why would Debden increase the jet sizes when only changing the ignition and useing a k&n filter. Weird! This, I think, is the likely cause of the sooted plugs.

Checking the voltage to the coils is easy if you have access to a volt or multimeter. With the ignition on put the meter pos to the yellow/red dual connector under the tank and the meter neg to earth. Ideally you want 12+ v reading. Ie the same as if you put the meter across the battery poles.

Plugs https://www.sparkplugs.co.uk/amfinder/? ... ---8096264

[John Reeves]

Thanks Warren, i'll take a look at voltage later.

Spark plugs, the link offers me standard or iridium, which are you recommending ?

[warren3200gt]

How deep are your pockets? I go standard cos Im 1/8 Scottish.

[AlanB]

Hi John - I see you are in Middlesex too.Good to see another member nearby and maybe meet up at some point !!

[Philippe]

Hi John
welcome to the club!
I hope you can get your A4 running in a decent way.
Show us some pictures, we all like to see those.
Greetings from Belgium
Philippe

[flateddie]

welcome in John, I had my z1000a1 running rich found the choke springs were a bit weak and not returning correctly, good luck with the carbs and +2 for the Denso plugs they are a lot better than the NGK's

[John Reeves]

Thanks people appreciate all the advice, I'm working through your points (when my wife's "Jobs to do" list allows) and will update once i get it running properly.......

[ZedHead]

Just thinking a little left field.

I notice you described the plugs as oily? .. Is it un-burned fuel or oil? What are the exhaust emissions like? If smokey, what colour? Is it at start up or on overrun? If it is burning oil I would tend to suspect the valve stem seals have failed.