The restoration is
never cheap and generally in the long term the value is below the equivalent bike preserved, even if it you spent more.
In this area of the site you find a summarization of the costs and work of a full restoration: specific information will be reported in the technical areas.
Consider the following extimated costs (in Italy):
Then there are pipes, cables, wheels, discs, pads, steering and swingarm
bearings, saddles cover and many other parts that may be missing or that need to be replaced or restored that drives up costs further.
For this reason a nice preserved complete is to be considered as the best base to get a nice bike, reliable and restored (the so-called "conservative restoration") in full compliance with
originality and with reasonable costs.
Regarding the engine you can find people offering "rebuilding" for 300 €, but only the seals and bearings cost at least 100/150 €. Is up to you to trust and accept the possibility that the newly overhauled engine does not exceed the first runnings, you must change the clutch plates after a little or the plastics sprockets broke. Just keep in mind that a lot of people measurethe cylinder, choose the piston size and trust in the box without measure also the piston. Sometimes this make the piston to be too big and it seizes. A job well done takes time and costs more than a merely bearings subsitutction: work out of tolerance wear the bearings and also the placements of them in the crankcase and on the crankshaft.
The same professionalism and the related costs made a the difference between a good and an excellent paint work or between the only change of the fluid of the fork and its fully ispection.
I think the do-it-yourself can be a way for routine maintenance, but for a lot of works expertise, experience, equipment are needed. Try to see a fairing (real not a the picture !!!) painted "at home" or by a shop specialized in motorcycles...
As for maintenance also the restoration will be taken at the appropriate technical areas and there will be constant improvement, so visit regularly to enjoy the news!