As stated above, stainless is not as strong as 'regular' steel bolts.
I say 'regular', but there are several different tensile strength classifications;
4.6 4.8 5.8 8.8 9.8 10.9 12.9 the higher the number the stronger the bolt.
Most common are 4.6 8.8 12.9, these numbers appear on the top of many, but not all, bolts. As a guide, stainless A2 and A4 would be ROUGHLY equivalent to 4.8
As for suitability on mopeds and similar I would advise the following;
DON'T use them on strength critical fittings such as shock absorbers.
DO use them on cosmetic stuff like fairings and on items where strength is not critical such as mud guards and luggage racks.
Use your own judgement on other items.
Maybe not a good idea on an exhaust that only uses one M8 bolt, But probably fine if the exhaust is held on with 3x M10 bolts
Hope this helps! Adrian
P.S. my first road legal moped was a 1981 FZ50 in red! (edited)