Running very rich at idle

Hey blokes,

I'm trying to sort out a couple of small items, main one right now is that she is running rich, and using a fair bit more fuel than usual (although it seems ok when driving), it mainly seems very rich at idle.

I don't have an afr gauge, but I have adjusted the idle to where it seems happiest, best idle speed and driving performance etc. and doesn't seem to blow any fuel smoke when revving.

Air filter is not too dirty, timing is at about 15 degrees from what I can see, Carbie was rebuilt professionally last year. In addition I have checked the auto choke operation as per photos below.

Photos show the alignment of the choke, the butterfly when cold and after reaching normal temp. I can take it to the fella who rebuilt the carb for me but I do like fixing stuff myself.

Any ideas what to look for / at to track the problem down?Attachment 71649Attachment 71650Attachment 71651

Hey mate,

Looking at the pictures your auto choke seems to be working fine.
You can turn the auto choke anti clock wise a little bit during winter, but probably not necessary.

But, I can't understand how a reconditioned carby that was done around a year ago look like that in those pictures.
It should look bit more mint for a carby that was fully rebuilt around a year ago.

Assuming yours is a straight petrol, I would stick with factory recommended timing of 12 BTDC or less.
15 and above is ok if you either use 95 or 98RON or LPG. Unless yours got LPG and ignition is timed for LPG, putting 95 or 98RON is waste of money in my belief.

I would take the carby(or the vehicle) back to the bloke who rebuilt it, but if you wanna try to adjust the idle mixture DIY do as below.

Follow the below procedure to adjust the mixture screw on idling

Start the engine and run it until it's fully warmed up.
Turn the mixture screw all the way in and then turn back four turns.
Then adjust the idle RPM to around 850ish(use fast idle screw, it's to the left & above of the idle mixture screw)
Then keep turning the idle mixture screw in until you get the highest rpm.
THen adjust the idle RPM back to 850 ish.

Now, take out the first or second spark plug and clean it properly to remove all the soot.
Then put it back and run the engine on idling for few minutes and check the spark plug again.
If there's no soot, then you can reasonably assume the idle mixture is on stoic and it's not running too rich.
Now, if you go for a short drive around the block and check the spark plug again & if there's soot, and
then probably cruising and WOT is still running rich. In that case adjusting idle mixture won't help, and carby need a
proper rebuild by a carby specialist.
If the idle mixture is still running rich after checking the spark plug(soot on it), then you can keep cleaning and putting the spark plug back in and turn the idle mixture screw a quarter turn at a time(in to start with and out if that doesn't work) and check the spark plug for soot.
It can be bit time consuming, so if you have a Gunson plug, it's lot easier as you can see the combustion flame directly through the Gunson plug.