mk1 1.3 carb fed problems!!GRRRR

Hi everyone, ive got a 1.3 fed by a solex im pretty sure.
The car wouldnt run below 1000 rmp since i tuk her on a run for probably 60 - 70 miles.
I may be wrong but one of the spark plugs i cudnt remove as I cudnt remove it without taking the bottom off…and i didnt want to have to take the cylinder head off just to remove the plug bottom.Could the old spark plug gap be increasing as it gets hot , causing it to stop running below 1k rpm????????The other 3 are new plugs.

Jet blocked???
fuel pump???

Thanks,
Any  help im grateful for
Rich

taking the head off still won't allow you to remove the spark plug - it has to be unscrewed from above.

I would suggest the plug is the cause of your problems, not the carb

yeh i mean if i unscrew the top and the bottom drops into the cylinder ill have to remove the head to get it out………..

Rich