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Long time lurker and first time poster,

G'day from Australia! I've recently purchased a mostly restored 1980 Z750E with a service manual! Restoration has been over several years or more and bike was still not on the road. Engine is rebuilt and 810cc and carbs have been done also and I've just added Dyna S ignition as the old igniter was fried and old mate had not replaced the original ignition or rectifier. I'm pulling the carbs off to clean as the bike has been sitting for a few years. I've searched the forums here and found some great info thank you guys. I've downloaded the diagrams on where the air should go in and out etc when blowing them out. Carbs are off and completely stripped and will clean them tomorrow. I have a new air cleaner, original airbox, new carby mounts on the head side and original from carby to airbox though they look good and are flexible with no cracks. We didn't have that air injection thingo in Australia but I see provision for it and there's some kind of valve thing with a hole going into the airbox at the top and the hole goes straight through.

Finally got the bike to fire up with a fair bit of throttle and won't idle. If I screw the idle adjuster right up it will idle at 2000rpm but then if you rev to say 4000rpm it will hang at 4000 for ages then slowly go back down. Number 3 cyl is not firing at all and it has plenty of spark so no fuel getting in there. Once the bike is warmed up it either wont start at all or its full throttle like starting a flooded bike. I pulled the plugs and the 3 cyl that are firing are black soot. I'm guessing from what I've read the idle circuits are possibly blocked or not working? It's getting way too much fuel, wont' idle and seems to be happy above 2-2500 rpm except for cyl 3 not firing. The carbs butterflys seemed to have been bench synced and I will sync them with gauges when I can get it to idle and check the fuel levels on the bench also. Number 2 carb supplies the vacuum for the petcock, the other 3 are plugged off. All idle mixture screws are currently at 2 turns out. All the parts look good inside the carbs and they look clean and looks like new diaphrams and needles etc.

Do I need to block off any open holes on the airbox i.e. where the air injection would go (we don't have in Aust), where the overflow tubes go in the bottom?
Do you think this sounds like the primary or ilde circuits are blocked?
The carbs sit on a slight angle on the bike, are the fuel levels checked with the carbs horizontal on the bench?

TIA guys!
 

Did you remove both the pilot jets and bleed pipes?  Hold them up to a light to make sure the tiny orifice is open?  Remove the pilot screws and shoot carb cleaner spray down the pilot passages to make sure they are all open, especially the passage by the throttle butterfly?

Hi Nessism, 

Thanks very much for the info. Yesterday I stripped the carbies completely and cleaned them out. I have checked all of the orifices mentioned and to be honest none of them seemed blocked. Carb cleaner ran out everywhere it should and so did the compressed air. The only weird thing I noticed is that 2 carbs were missing the springs under the pilot screws. Initially I thought this would change the height of the setting but it actually doesn't, it just means they will eventually vibrate to a different setting without springs. I will be putting them back together in the next few days and see what happens. 

Oh and yes I did remove all jets and bleed pipes. Nothing looked blocked but I cleaned them anyway.

The pilot screw spring is critical, because it pushes down on the rubber O-ring and makes sure it's seated/sealed.  The order of assembly is first the spring, then the tiny washer, then the O-ring is inserted on the pilot screw.  When removing the pilot screws, the spring, washer, and O-ring will often stay down in the threaded passage.  I use a small pick with a J shaped bent into one end to fish out the pieces.  

All the various O-rings must be changed when rebuilding the carbs.  I've posted the sizes here on the forum at least half a dozen times before, so search out the info if you don't already have a full set of O-rings.