You might get close to narrowing it down. Pull the tank and in the frame beneath the tank is a label if it is still on the harness and it has a month and year of when the harness was made.
Early S90 has a 45 degree header pipe with one piece
The later had a 90 degree header pipe with both one piece as well as discrete header pipe and a muffler. Last build were one piece with 90 deg header.
Mount points vary on the muffler so beware.
Many parts are S90Z parts many do NOT work for the earlier bikes.
The Honda Parts manuals are screwed up so sometimes they quote the wrong part number. Early bikes had the 3 cross spoke pattern and later went to the 2 cross pattern and the spoke lengths can be wrong on the spoke length.
4 or more engine gaskets sets are out there...so beware on that too...
Simple motors capable of 8hp if it wasn't a Nevada 5hp or other funky one...
The cam was not the same as the CT90... head changes too
The carbs had 2 variants if not three...
offset carb or centered carb on the intake
Couple different variants o fthe airboxes based on the offset or centered...
The last domestic was a chromed big cylinder with centered input to the filter box.
Front forks had differences base on years and way you take them apart...
Battery door is rare as hens teeth and expensive if you have it keep it guarded...
Frankenstuff makes one for it and airbox end caps if you have the big painted endcaps IF you can talk him into pulling you a set from his molds. Shouldn't have to twist his arm too hard if you ply him with enough cash if it isn't too busy. Frank makes some nice stuff. Talk to anyone who has his sidecovers and they will tell you, top shelf quality pieces.
Yahoo S90 group is worth joining to tap into their vast knowledge resources...
David
