NA20 Carb issues?

[Rex Calibvr]

Hi all.
I just bought another 1990 Nissan Navara na20.
The previous owner had just had the carb rebuilt, butit was idling really high cold and warm, I have adjusted the idle, but here is the big issue..... it is using a tonne of fuel, and tends to lack power and will often stutter.
I have made small adjustments and can get it to run smoother, but I don't know much about carbs and am scared to adjust things too much.
From what I could find the mixture screw should be out 1&1/4 turns roughly. But I checked an old engine in the shed and that was at 6&1/2 turns out (am not completely sure I have the right adjustment screw either) but this is a slightly different carb.
Any help would be greatly appreciated and labelled pics would be awesome.

Thanks in advance

[zukmeista]

Does it have an auto or manual choke? If auto it could be sticking closed which would contribute to the issues you describe.

[derk]

the mixture screw only adjusts the idle mixture the main jet inside the carb controls the normal fuel mixture so the idle mixture wont be causing the thing to use excessive fuel, lack power or splutter

to adjust or re-adjust your idle mixture get the thing up to operating temp and adjust the idle control to get the idling rev's you want, then wind the idle mixture screw in until the engine starts to falter then wind it back out 1/4 - 1/2 a turn till it idles freely again

To find out why its running like a bag of shit you want to give the thing a service and tune first, check and/or replace ignition, plugs, leads, timing, mechanical and vacuum advance, (points if it was a few decades older ), fuel filter, vacuum leaks, compression test if your mates got a tester you can borrow, etc , once you've been through all that stuff you'll know if the problem is the freshly rebuilt carb or not

[Rex Calibvr]

Thanks,I found a stuffed spark plug earlier, running a lot better now, no sputtering etc.
It does blow abit of white smoke
Would the spark plug cause excess fuel consumption? Or do I need to look further???

I will post a pic here once I work out how, carbs have too many screws and adjustments for me!
If anyone can tell me whats what it would be much appreciated.

Thanks for the advice/help

[Rex Calibvr]

And its an auto choke but that seems to be operating ok

[Rex Calibvr]

Could someone tell what the blue and green circled screws do exactly.
They are on the drivers side of the carb.
Picture 3, need to enlarge to see circles

[derk]

looks like blue = idle speed and green = idle mixture

is the blue screw the stop screw on the throttle linkage

[Rex Calibvr]

No blue goes into the housing just in front of the throttle leaver, located at rear of the carb.

Stop screw sits on a white plastic (kind of hour glass shaped) piece, which is controlled by the auto choke located at the front.

Does that make sense?

[Rex Calibvr]

But yes blue did adjust idle speed depending on the mixture.
I actually altered the stop screw first. Now that's a pig at even with air filter and housing off

[Rex Calibvr]

So the issue was:
1. Slightly high float level,
2. Choke wasn't fully coming off
3. Hot gas inlet from exhaust was staying active

So disconnected 2&3
Fixed the float lvl