My 2 cents worth buy a proper SU pump stop fiddling with non standard items .

Maybe sticking due to the jet not being centered correctly and that is why the needle was filed/sanded.
You maybe got lucky with the other parts installed sometimes you can turn the top around 180 degrees and they end up being centered easier.
When you install the new jet center the jet with the spring and adjusting nut removed also dont install the jet tube in the float chamber until final assembly.

Now too much fuel is the problem again; I took the advice of Mr. Moke Caldwell, and checked the float and jet.  It passed, but seemed sticky on dropping to resume fuel flow.  I had a repair kit for an HS4 with a grose jet and seat, so fitted the new parts. My old and untested parts carb that came with another 850 I got some time ago had a much smoother operating piston and dashpot housing, amd already had a clearly marked EB needle in it.  Dropped those on top of the carb in the moke, and a test run aroind the neighborhood acted as good as the day we got the car.  Not perfect, but so much better!

A new jet assembly will be ordered Monday, and then i can get back to the other list of stuff to fix on the car....

So, after some more aggravation I think i have solved a few issues, and hopefully am well on the way to a fully functional moke again.  Wire brushed and carb-cleanered the old plugs, which were the Champion N9Y's.  I thought things were going better, because I was able to get a blue burn at idle out of the colourtune.  The test drive resulted in decent power, but it stalled every time I came to a stop.  The timing light let me know the vac advance was working, and just on the lifting pin travel the piston was falling with a clunk.  It wasn't until I took off the air cleaner and gave it a full throttle shot that I found the piston was sticking at the top of its travel.  In the process of fettling, I fitted a pressure regulator with a gauge, and a new clean and clear fuel filter.  Thanks to the trickles and bubbles visible in the latter, I found that the electric fuel pump on the firewall was not keeping prime- probably because the old, non-working Facet pump was still in the fuel path in the driver's side companion box..
Removed the box pump, moved the working MrGasket Micro pump down to closer to the tank, and hey, look, the fuel filter is full, and now we have enough gas to foul the plugs again...

Order the carb parts here from Joe Curto in NY.
BPR 6ES or N9Y plugs should be fine in an 850.
Make sure everything is set correctly points, plugs, vaves timing etc before touching carb adjustments.
Also check that the mechanical advance is working on the dizzy.

travelling. you are using the right NGK plugs..  might try BPR8ES..

1. The last set of plugs i put in were NGK BPR6ES.  I will see if any of the local stores have a hotter plug to try.
2. I have another carb with the correct needle (EB) in it, but that carb was given to me as "in need of a rebuild", and the choke cable attachment is different, so just popping it on there isn't likely to improve things much...

I can place orders on the jet and needle tomorrow and then check back in when things arrive.

Fit a new jet and centre it properly.  Look up in the Book of Words the correct needle for a standard 850 and fit one.  (Order direct from Burlen).

Set the jet 15 flats down from flush as per the manual.

With the engine running check the vacuum advance & retard unit is working correctly.

Set the timing with a strobe and the vac disconnected.

What plugs are you running ?
Sounds like they may not be hot enough and are fouling at tickover.

I'd have thought that a NGK BP5 (maybe a borderline 6 but no colder) or a Champion N9YC would be suitable.

travelling.  did you think about just buying NEW carb?/  damn cheap at Burlen fuel systems in the UK.. I NEVER rebuild carbs anymore..  too much hassle.. later bc

On our 850 Moke I am having a lot of trouble telling if I am getting the carb set correctly.  It is an hs2 with the stock manifolds and air cleaner.  It has carbon coated the plugs in a very short run of time (less than an hour of driving).  I have replaced the plugs a couple of times now and it's getting a bit of an expensive process to take it out of the garage. Idling has always sounded a bit off, with the exhaust "woofling" every now and then, not quite every engine rotation, but certainly a few times a minute.  I have heard no pinging under acceleration, so all signs point to too rich.  I leaned out the mixture several flats, and had almost no change in idle speed or lifting pin behaviour during that process.  

I took the dashpot cover and needle housing out, and the needle looks to have been sanded on at some point in its history, but could not find the identifying numbers on it anywhere.  Once lined up on the keyway, the piston drops to the bridge with a clunk, so it's not obviously sticking there.

The choke is sticking on occasionally, but I can pop it up the last tenth of an inch by hand and have done so before any of the testing/adjustment.

When it is idling-using a borrowed Gunson colortune- it is showing yellow= rich, but the moment I move the accelerator even the slightest bit, it goes bright blue, so the mix can't be miles out.  Using the lifting pin yields not much more help, as it seems half the time it accelerates slightly, and the other half (especially if it is woofling) it slows down to the point of dying.  Is the lifting pin supposed to be a momentary thing, or should I be holding it up when looking for the results?  So far I have been holding it up, as just popping the pin up and letting go gave no change in engine behaviour. 

It is on a Mr. Gasket electric pump, and on the theory that the pump was overfilling the float bowl with too much pressure, I have fitted a pressure regulator and gauge which verifies it is at 3 psi running.  Fuel is fresh and recently topped up, no vacuum leaks are in evidence (tested with carb cleaner spray around both ends of butterfly valve, and around manifold to carb junctions.  The fitting at the end of the vacuum advance line at dizzy was cracked, so that has been replaced).