Hi Lachlan
I used the reference below to get started:
https://tecb.eu/onewebmedia/Tuning_SU_Carbs.pdf - Section III Tuning Multiple Carburetters
Also a really good section on tuning in this:
https://www.amazon.com.au/Carburettor-High-Performance-Manual/dp/1787111687
The pdf above is a good starting point, but I found the following things, which were not necessarily in the instructions, but were covered in the second manual, critical to getting things to work:
1. Fuel levels in each bowl must be at the same height. Let them fill up, take the top off and physically measure the level. I used an electronic vernier calliper to measure this accurately.
2. Height of jet below the bridge for both carbs must be the same. Again, measure with the callipers at step 17.
3. Each carby has to be adjusted individually, so critical to slacken both the clamping bolts as per step 19.What you do on one carb, adjustment wise, you have to duplicate on the other.
4. You might be able to adjust the suction using the pipe as in step 20, but you are better off getting one of these: https://www.weberperformance.com.au/product_info.php?products_id=7 which you can get off eBay as well.
Good luck. It 's easy once you've done it and got it right, but getting there can be a challenge.
Paul