If you need technical information or help with your early crossover gearchange squarecase Ducati 860/900 engine - post your FAQs, comments & questions here.
Can someone with a vernier calipers and an accessible Ducati 900 bevel twin be good enough to measure the outside diameter of their stock header pipes?
If you don't get a reply from someone with a 900, my 750 headers are 42mm OD, and I think the exhaust nut and mufflers interchange, so there's a pretty good chance that the 900 is also 42mm.