Here is a download page where you can find the Yamaha Mio 125 Parts Manual from Yamaha. I had a helluva time finding it, so you shouldn’t have to go through the same.
If you want to know how to adjust the idle on your Mio 125 – just lift up the seat. Remove the rubber seal on the hump there. Use a long screwdriver and turn the screw clockwise to cut the engine RPMs a bit. Turn counter-clockwise to let the engine rev a little higher at idle.
or, if you just want the catalog, you can download it at the link below, keeping in mind, this is a PDF document, and it starts downloading immediately. If you want to save the PDF, you’ll have to hover your cursor over the document as it opens in your browser, and then choose “SAVE AS” when the link shows.
Yamaha MIO 125 catalog