Hi 70'S VINTAGE
Over the years, I have restored many bikes, mainly British,but also some Japanese. The question you ask is a familiar one to me, and I have had many conversations with prospective restorers over this.
If (like me) you enjoy working with your hands, have a (dry) garage, basic machinery which allows you to make/repair components, and a lot of patience, then restoring a ST 70 is a very satisfying project. The finished product which you have created will give you great pride and pleasure.
HOWEVER
Take into consideration the following:-
Your time involved
Cost of Parts
The standard of restoration you want
Phone calls, Postage, Cost of Travel to drop off or collect Parts
All the above adds up very quickly and is costly.
My advice usually is, that if you want a particular bike, then look around for a complete finished one which comes up to the standard you want.
A bike which the previous owner has spent a lot of time and money on, and for whatever reason now wants to sell it.
To restore a bike yourself is great BUT you will never get back the time and money spent--------just satisfaction that you did it your way.
I restored our ST 70 3 years ago. Parts are available and I had them from all over the world,some cheap and some very expensive
As to your question of how much you could expect to spend? Sorry I can't answer that as I kept a log to begin with, of the costs involved
(not including my time) , but had to tear it up in case the wife found it!!!!!!
P.S. PAINT OR POWDER COAT?
Paint for me every time. The slightest spot of rust will eventually lift the powder coat which is then very difficult to touch up.
To get a ST 70 pressed up frame with all its seams,nooks and crannies rust free is virtually impossible.
Hope this helps,
Ken