mk1 1800 misfire problem/twin carbs

as above really, not new to a mk1 but this one has been bought as a track project and is running 45 carbs, stainless zorst etc. picked it up last night finally and was told it had a lil misfire and prob needed plugs as its had very lil use lately etc. so drove home on what felt like 3 or even two at times and today i've been having a look. changed all plugs first for brand new ones, no change. found the dizzy cap on wrong and not sitting flat as the lug was not in its cutout so thought that would be it and duly sorted it. no joy, sounded better but a quick drive told a different story. then pulled each plug off and found number 2 to be the only one making no difference on idle. bingo. or so i thought. changed it for a known working plug lead, x3, still no joy. took the plug out of two and swapped it with one, still the same. now i'm thinking its a blown or burnt valve?  can anyone else shed any light on it before i take the head off please?  i've checked the cap and rotor and both look almost new as i was told they indeed were.

Blown or burnt valve could be diagnosed by a compression test - the pressure will be unfeasibly low for that cylinder. It could also be valve clearances, if its a non-hydraulic head (what engine does it have)? Also it could be a fuelling issue, since it has (you don't say but I'm guessing) twin carbs each with twin venturis, effectively each cylinder has its own venturi.

Moved to big block carb engines  :wink:

Id be inclined to have a look at the carbs before going any further in.

Could be something as simple as clogged jets.
If these are dcoe/dellortos  then they also have to be balanced.

Be aware that if the previous owners had them to bits the jets could be mixed up- have seen this before.
best to get a manual for the carbs and have a nosey in there just to eliminate that possibility.
If thats all ok then youre into compression/leakdown tests and stripdowns.

thanks for the replies so far chaps, it looks like it could possibly be a leak on the venturi going into cylinder 2 on the first carb, have sprayed carb cleaner across the inlet and it raises the idle speed when cold, slightly less when warm but obviously things expand as the heat up. i'm gonna look to replace all of the gaskets on the carbs first(yes there are two x 45's) and see if that cures it. it doesnt seem to be a random firing cycle with the king lead off as you'd expect with a leak valve side, seems quite normal so i'm hoping its the carb inlet to that cylinder causing the misfire. was hoping to make it to the meet sunday to but not sure i should risk it now.