What's going on? Valve job?

Save your self some tedium and just boil the carbs vinegar which dissolves the zinc oxide being precipitated on surface that gas oxidizers likely accelerate, but can form in just plain air oxygen. Filters can't prevent the chemical crusts.

Ok Guy's thanks for all your suggestions,i am going to pull the carb again and go through it again although i'm pretty sure the jets are all clear.I might go up to a 40 pilot and see what happens!!???.................Cheers Andy. ps can the diy spannerman perform a leakdown test?

Plugged pilot circuit. You should only need the enrichener circuit on for 30 seconds maximum. I have a 36 mm Mikuni and started out with a 35 pilot jet but now run a 40.

Gday Hobot, boiling alloy in (white?)vinegar does it have any discolouration affect on metal?
Foxy

No discoloration just cleaning to base metal w/o removing metal just the oxide crusts. The carb Pot Luck metal can polish up shiny but not brighten basic elements.
Vinegar is weak organic acid, use white vinegar/acetic acid to avoid possible staining of the Soup Pot of the day carb alloy. Norton heads are also a dull alloy.

Just spent a considerable time this week going over the Amals on a nice 750 roadster I bought recently, ran rough as hell, after ignoring all the advice I've read and given myself I started from the beginning, despite these being only 700 miles old (in 5 years though) I found different main jets (a 220 and a 200) needles on different settings, float heights wrong, sticking slide (prob a twist in the body) and very blocked pilot circuits. Now all sorted and running sweet but its no wonder I swapped out to Mikuni's on my other Commandos a right PITA to work with!

Oh and the timing was out, the Boyer ignition pickup was actually bent!! never seen that before and had been "repaired", luckily I've got loads of Boyer parts in stock since I changed out most of my bikes to Pazon

Do yourself and your bike a favor. Install a cable operated enrichener assemby and make up a cable to fit the stock choke lever. Remove the bowl, the enrichening circuit pulls fuel from the tube cast in the bowl. the fuel enters through a hole large enough ( rich enough) to start a large 2 stroke, Too large when attached to a Norton twin. the hole can be drilled and tapped for an Amal pilot jet, #35 . or you can plug the hole with epoxy and then drill a hole about 20 thou through it. reducing the gas entering the curcuit cures the 8 stroking and the bike will fast idle on full "choke" at a smooth 1600 to 1800 rpm, and can be adjusted down in increments with the bar mounted lever. Worth doing!!! Rick