more about SU carburettors

[Perseverant]

Just in case this is any help! I've had my XK120 for around twelve years now -great fun! However, when I got the car it had rich needles and tended to fluff plugs. Standard needles helped, but it remained a bit temperamental when cold. I've worked on a good many twin carburettor arrangements but have never been happy with this one, until a few weeks ago when I decided to check the initial settings with the vacuum chamber and needle assembly off. The back jet sat noticeably higher than the front one, so I set them both flush with the bridge before making the initial setting. So far all has been well - starts easily, pulls like a train and so on. In the past I'd stripped and rebuilt both carbs. but never thought to visually check where the jets had ended up when I started to set them on the car. I'd also set the linkages carefully too, so this recent development has ended up as both a solution and a bit of a puzzle!