HIF6 carburettor - a tale of smoke and mirrors

[Mr Spigot]

I have just completed fitting an HIF6 carb to my 1300 midget engine, replacing the single HS4 that was there previously which seemed to have run out of puff. Having carefully stripped and rebuilt the HIF6 with new gaskets, needle and butterfly valves, new K&N filter and got all the cables finally fitted in the right place, adjusted the choke and idle settings and the jet adjusting screw, I turned on the ignition and pulled the starter knob.
To say it spluttered into life is perhaps an exaggeration, as it fired occasionally, spluttered and popped a few times and with the choke pulled right out it ran, but sounded terrible. It was if it was only firing on 2 cylinders and surged faster and then slower, popped a few times, sent out puffs of smoke and as soon as I touched the accelerator, abruptly stopped.
Clearly something was wrong! I checked everything carefully again, took out and cleaned the plugs which were a little sooty but otherwise fine, checked all the leads and even took off the distributor cap to check the timing was not 180deg out, although it had run fine with the old carb. I static checked the timing and it was spot on. I then decided to take the dashpot off to look at the needle and jet to see if there was anything amiss there. Once the piston was lifted out with the needle out of the jet, I noticed that the top of the jet was sitting proud of the bridge. The manual clearly states that the jet needs to be initially set flush with the bridge and then the jet adjusting screw turned 2 times clockwise to lower it. I had done this, or so I thought. I then realised the source of my error.
The jet adjusting screw is set low down on the back of the carb, facing the fuel pump. It was difficult to see, let alone guide a screwdriver into it, so I had placed a motorcycle mirror at the back of the engine bay so that when I shone a torch on it, I could see the screw and get a screwdriver in to turn it. While I thought I had turned it 2 turns clockwise, I failed to realise that I was looking via the mirror, so ended up turning it 2 times anti-clockwise, thus weakening the mixture significantly. Once I reset it flush and then lowered it by screwing clockwise, put the piston and dashpot back and tried again, it fired up straight away and with a bit of adjustment to the choke and idle screw, settled into a steady tickover. It still needs some fine tuning when I can take it out and run it and get the mixture spot on, but how relieved I was to have found the fault! The photos show (not that clearly) the screw in the mirror.
I hope this may help others replacing carburettors who reach a similar problem!