Honda-SOHC

Just to clarify couple of points - I've had it running before, although very briefly and very rough -  and I am pretty sure cylinder 1 was running OK (although not long enough to get any real temperature into it) - when I said I couldn't get the spark plug out it's because I didn't have a socket/box spanner - so as far as I know it should come out when I get a chance - apologies for the confusion - I have ordered a compression gauge so I can check all cylinders anyway as a general health check - lesson learned - should have done it before taking carbs off etc -

Hi all - been a lurker on here for a while- this is great resource -many thanks to all for the info - its a massive help - currently restoring 76 400F and have hit a problem with trying to sync the carbs as I cant get a vacuum on Carb#1 - background so far - apologies for long post -
Bike was a non runner when I got it late last year - got it running but very rough running, wouldn't idle -
Stripped carbs completely , very badly gunked up - ultrasonic clean and vapour blast - reassembly - ( have used aftermarket brass except for float valve where I used the original OEM valve ) - first attempt with aftermarket float valves resulted in leaks on all carbs -
So this week tried to sync carbs using vacuum gauges - carbs 2/3/4 all pretty much spot on from bench sync - but no vacuum on Carb 1 - can move the gauge if I suck/blow on the line - so not the gauge -
I have sprayed Carb Cleaner around all the inlet rubbers and carb tops whilst its running which has had no effect - no rise in revs or stall - so I don't think there is a leak at the inlet / carb tops
Header on cylinder one just warm to the touch where others are hot from running - so I guess its not running on cylinder 1 - couldn't get the spark plug out yesterday so have not checked if its getting a spark - but my question is -
is there anything I could have screwed up so badly rebuilding the carbs that would cause vacuum loss on one carb ? - also noted that is starts from cold without choke - so assuming its too rich, also idle screw is turned out so far its no longer in contact with the bar at all - I am hoping I have messed up the carbs/bench sync rather than it being a bigger problem - but could that cause no vacuum on one carb in isolation ?