Here it is folks, the dimensions for the adapter plate to fit big carbs to the 500ís. It is possible to use other types of adaptor but this is my preference. Made from aluminum alloy, they look like genuine Denco manifolds. All you need is a set of carbs and the rubber mounts. Both of these are obtainable from Allens Performance of Nottingham. To machine the tapered bore you will need to run the block off centre in a 4 jaw chuck. The rest can be done on a vertical mill or even a pedestal drill at a push. I drill the main throat hole to 25mm and use a clock gauge in this to line the block in the 4 jaw. To finish them you will need to bolt it to the cylinder and the 28.28 mm end will need to be matched to the inlet port shape. This is easily done with a Dremel type thing. I use one piece carbide cutters. These remove metal at a massive rate of knots and the ally doesnít clog them. To make 34 mm carbs work properly you will need the rest of the motor ported and a good set of chambers.