Watch-out for this one, lads !
I decided that I didn't like my 102 mains as supplied with the Keyster re-build kit (PD 44B carbs) and today decided to go back to the 108's that were in the bike when I got it. The 102's being, i.m.o. just too lean, producing a light gray plug, and a possible over heat now that were facing another Summer etc., blah, blah.
I put back the 108's and the old needles, fired-up and #4 smoked like mad and eventually fouled the plug..luckily #4 float bowl is accessible...everything was perfect in the bowl.
Turned-out that in taking-out the carb. slide I had rotated the carb. bank for some reason and when I dropped the slide back in it was facing the WRONG way with the cut-out section facing into the carb.!!! There is no 'keyway' and slider will go in either way quite happily...slide reversed= very rich cylinder !!!