There is blue prints of the frames for these, some posted here and in the tech section, but a google image search brings them up, Ill try and post one, but simple task to measure. We have a laser for leveling and construction work we got at Harbour freight,, My drainage pipe project (300 feet across the property) worked so well in 15 years have yet to have to use the cleanouts I installed.
You can use a laser or string to also chart out your measurements. The longer the string or line, the easier to measure discrepancies. 2 long straight edges on either side of the tires is a good judge,, We use to set up side cars for Urals at a shop, Some other brands as well. A bike for sidecars has different setups than a solo bike and not aligned right, is a nightmare to ride.
Old bikes are most certainly tweaked but some were easier to prang than others,, a Commando tweaks its frame if a curb is even in the vicinity,, (Flexy they are). We sent out a old preunit Triumph (57 TR6) that was raced extensively and it was crooked in 18 ways according to the frame shop. At that time there was 2 shops in the US that used lasers and had their setups,, one was local. Owner was challenging so I wanted no questions about the frame.
It just depends, some parts are castings which you CANNOT bend or move, and then all that tubing, often hearth brazed into place,, All of it is adjustable to a degree.. There USED to be on InAccessibleNorton a thread called "Worlds straightest Norton" and some does not pertain to other bikes but it was an excellent tutorial on setting up a bike to run straight and true. A lot of people still ask for it but it vaporized last I heard. Was watching some Old Indians and Harleys racing and rigid frames and was amusing to see 70 year old frames flexing at high speeds on the race track. There was a local that WAS racing a HD 45 mtr with BSA box in a Norton featherbed frame on the vintage MX circuits,,, That was FUN to watch that thing..
it was a fan favorite seeing it go off jumps and shooting dirt in the air.
