Please help, before I go hang myself

[Potts]

I am at the end of my rope about now and am hoping someone out there can help me, or put me in contact with someone who can. This is a long winded story but please read on.
About 9 months ago I bought a '76 z900 in boxes. Some of the parts had been restored. I went right back to every last nut and bolt and everything has been restored or replaced with new without regard to cost. I now have a pristine bike that is simply beautiful BUT runs like s**t.
Once everything was back together it fired almost instantly. 2-3 miles up the lane and all was good. Not perfect and a bit difficult to start from cold but once warm seemed pretty good. I set the ignition timing by the book and then started to try and balance the carbs. Little by little I have got further and further away from a good running bike. It became obvious there was a problem with the float levels in the carbs. I duly sent the whole lot off to Steve at Motocarb. He rebuilt the bank with all factory parts and new jets (apparently there was a bodge of aftermarket and mis-matched parts). Refitted the carbs and no difference. Needles up and down and I couldn't get it right.
So today, the bike starts easily enough but once warm if I shut the choke below about 25% it stalls, pops through the carbs and exhaust and will NOT rev with the choke off. At about 1/3 choke all seems well but I get a lot of white smoke. Plugs are sooty, exhaust smells of petrol a little too. Seems like it's too rich and too lean all at once.
This is where I am at just now
Carbs are on standard settings throughout, VM26s.
Standard airbox.
V&H 4-1 exhaust.
Brand new wiring loom, coils (bought in the US), leads, plugs, caps, Boyer ignition. (Have had it running with a points set up too, no difference)
Engine fully rebuilt, valve clearances set. New rings in honed bores. Compression pressures a little low, I guess because it's only done about 5 miles and not bedded in, about 130PSI on all cylinders. Valves all recut and ground, as far as I know these are standard but looked like someone had given the head a clean up and polish. New cam chain and all new tensioner parts. Timing checks out as per the book. There's very little blow from the oil filler when running so I think the bores are Ok.
If anyone has any ideas or can put me in touch with someone in my area (Norfolk) who can help I would be forever grateful, i am at the end of my rope on this one. I even considered breaking it up again but it's so beautiful I don't have the heart.

[Tonka]

Hi, still sounds like the carbs.

I know a few guys/tuners who say that they can clean them and set them up ok but in all honestly you are best sending it to a guy who knows what they are doing on Z1 carbs. Send the carbs to gez in the post. He will strip them right down and send them back with all set up and ready to go. If you PM me I will give you his mobile number.

[Gavin]

When I last did a restoration I used new carb parts etc what I had was a sort of laquere coming away from the tank side and causing problems with the jets etc. the particles were very small and hard to spot an inline fuel filter sorted it out straight away.

[Pigford]

Also double check no air leaks in rubbers.
Make 100% sure you're getting OVER +12v to the coils when the bikes running
Try another set of new plugs - DENSO instead of NGK.
Run the bike in a dark garage and l;ook under the tank at the coils & lead for arcing.
Check kill switch isn't shorting out - run a power line direct from battery to coils? Even new coils and play up.

[garyd]

Not a direct helpful hint but I was rebuilding My GPz1100 A1 years ago with a big bore.

After reassembly the thing would only just start t and ran like shit.

I tore that motor down twice before I spotted that I had a Z1100 shaft timing advancer on it. No idea how I got hold of it but looked almost identical to the GPz item.

So the suggestion is, Check all the new bits the previous owner bought are exactly for an A4...

[Z903]

the particles were very small and hard to spot an inline fuel filter sorted it out straight away.

+1 to that. Fit inline filters, no one will really see 'em, and it will save a LOT of pain pulling carbs on and off.

[750steve]

Air/mixture screws set ok?

[chrisNI]

One time I had a problem with a bike running like shit, wouldn't run with choke off etc. had carbs off a pile of times eventually turned out it was accumulated gunge in the fuel tank blocking the gauze filter in the tap

If it's not that, have you tried borrowing a set of carbs off a working bike to see if it actually is carbs? With something like this that can be the best way to progress by eliminating things.

[Garn 1]

I would empty all fuel out and re-fuel.
Could be contaminated!
RegardZ.

[Potts]

Thanks for all the replies.
I will check the voltage at the coils.
Intake rubbers Etc' all new and tight.
2x inline fuel filters are fitted (been there before).
Inside the tank is pristine and the fuel flow from the pipes is good.
Air mixture screws are working Ok, a 1/4 turn makes a noticable difference to the running, got them all about spot on I think.
I have a set of what I believe are VM29s that look to be very good, no signs of messing about with them, pristine screws Etc, no corrosion and very clean unrestored (from California). Will these run ok no the 900? Will I need to change the jets to the ones from the VM26s?
I rechecked the compression pressures at the weekend and have 160 in the outer cylinders and 148 on the centre pair ????
I had the engine idling slowly (900rpm) with one of the plugs out. There seems to be a continuous flow of small sparks across the plug interspersed with a very bright one. Is this normal?

Thanks again.

[zman]

I dont know if you have seen my posts about my problems,
We could always have a cry in a beer.

im not sure if im finally coming to the end of my problems.
This may help you.I have found at least 3 problems that make it difficult to diagnose the problem.
First was vaule had not seated correctly.
fuel not flowing correctly due to a block in the fuel tap.
But the worst problem was an intermittent short in the engine stop switch This made a coil slowly break down.then blow the dyna ignition.
Electrical faults can be hard to find.
GOOD LUCK

[zedrider]

just seen something similar I see you have a boyer bransden system . they like there own coils and the plugs should be with resisters . in them . sorry about my poor spelling .

[zince]

Hi Potts

I have a few z1s/z900's and am based in Norwich so not far from you . I am no Z1 mechanical expert myself , although i do carry out some f my own basic servicing/some repairs . However, i do know a good mechanic based locally who may be able to help and is very familiar with Z's .

I would also be happy if you want to try swapping out some parts off 1 of my bikes to see if you can solve the problem with yours and save you buying parts without knowing if it will resolve the issue.

Please PM your contact info if you still need help .

Cheers

Vince

[Potts]

Thanks for all the suggestions guys.
Today I checked all the electrics, even the earth resistance. Everything is good, all the parts are new but best to check I guess.

I pulled the carbs off and replaced with a set of VM29s (I think) off a Z1. Nice carbs once I cleaned all the dust off. I doubt they had ever been apart. Primaries were smaller (15s) and the mains larger (117.5s) than the previous carbs. Anyhow, vastly improved running. Idle at 800rpm, lightning fast pickup and very smooth. HOWEVER :-((((

Still smoking like my old grandad used to. If it's left idling for a while it's not noticeable. But, when I pick up the revs to 5k (setting up the Brandsen ignition) it starts to smoke. If I let the revs fall quickly and then crack the throttle it makes a pretty impressive cloud of smoke. Peering in the plug holes the tops of the pistons look a bit wet, like oil, it doesn't evaporate when left.
Does it need a good run or do I need to look at a re-bore. If so what are my options? I am leaning that way.

Thanks again.

[Ginger Bear]

Have the valve guides been checked or replaced