Replaced perished manifold boots now v high idle speed

All parts need a long bath in carb dip or sonic cleaner to bring back movement and correct jet size.

If the pin in the top of the needle valve doesn't SPRING in and out of the body of the needle valve but does move in and out then its knavkered and you need a new one.
I'm not talking about the needle valve moving in and out of the valve seat but the valve (with pin sticking out of it) itself. The pin on the end should be spring loaded.
 

Thanks. It does spring out. Not with great energy but does come out quickly. I’m curious why the LH carb float springs up and has some bounce where as the float in the overflowing RH carb returns to its position but without the bounce? 
I posted a video earlier showing the difference. 

Internal spring could be full of crud or broken. 
Probably easiest to get a new one. 

The OEM Keihin or Keester brand float needles are best.  They are rubber tipped, and 40 year is a long time for rubber parts to live life in gasoline.

And obviously, all that rust and crap will clog up the carbs, including the float needle, keeping the bike from running right.

Scirocco wrote:

Some one totally botched the tangs on the floats, right needle stuck and frozen.
Carefully remove the floats and bent the tangs back to the same deck as the float holder surface as a new starting point.
Remove all jets, needle valves and bleeder tubes to clean the the brown rust sludge.
Also take a look into your tank and petcock fuel filter (could be clogged).
I use a bendable magnet stick to catch the rusty flakes.

~~~>>> That’s a great idea. I have all manner of magnetic sticks to pick up metal pieces yet I never thought to pick up rust with it. Good one.

Thanks all.

I'll order a replacement and let you know how I get on.

Nessism, I've found a 2nd hand Keihin, described as "Genuine KEIHIN carb part removed with care cleaned and de-greased IN GOOD ORDER":

**I can't post the ebay URL, but a search on ebay UK for "KAWASAKI ZX1000 ZX 1000 A1 A2 CARB CARBURETTOR NEEDLE FLOAT VALVE X 1 1986 - 87" will bring it up.
The part number is 160301007, which matches the part number for my KZ440 LTD carb.

The alternative is a brand new non-OEM: 

** I can't post the ebay URL, but a search on ebay UK for "Carb Float Needle Kawasaki K Z 440 A 1982-1983" sold by scooterandbikes will bring it up.

This is my only bike and I use it once a week to travel to and from town - saves on car parking charges. In Edinburgh that's a lot of dough and I've just found out I'm out of work end-March, so money is tight and time is tight - I want my baby back on the road by a week tomorrow.

I appreciate the points about further dismantling to clean all the valves, and removing tank crud and filter cleaning but I'll need to leave that to when I can spare more time. My only focus just now is to prevent the overflow. You guys have been fantastic with your advice and quick replies, I really appreciate it. I'm learning a lot here.

Genuine new parts in the UK.
www.allensperformance.co.uk/shop/

Thanks Warren3200gt.

Via Allen's, I contacted Craiglee Kawasaki and they have a 160301007 is stock. £32.50. Wow! 

FYI. Allen's said they cannot match the OEM product number with their part numbers, hence putting me on to Craiglee.

float valve Z440  5,90 €

Keyster = KVN-16R30
OEM = 16030-028 replace 16030-1007

www.motorradbay.de/en/kawasaki/sh-4.html
www.motorradbay.de/en/z440/p-2139.html

The keyster needles are good.  They have a proper needle spring, that can hold up the weight of the float.  All the other aftermarket needles I tried couldn't.

Jimbo, I understand the need to get your transportation on the road as soon as possible but until you have all needed parts in hand it’s going to take some time. It may be worth driving and paying the parking fees than throwing the carbs back in only to have to rip them out again to replace the damaged parts and to clean them properly. Maybe take a bus.
The tank and petcock and fuel hoses are also important parts of your fuel system. Without cleaning and derusting the tank (and adding a filter) all you're going to do is constantly send crud into your carbs and constantly have to service them. Rubber lines get built up crud inside them too.
Unless you fix it all at the same time it’s a never ending cycle. By my experience in anything, nothing takes up more time than a "quick fix".