If you perform a search for the rieju marathos pro 125sm and click on IMAGES rather than ALL, you will enounter a number of diagrams of possible interest to you. But you may have to search ebay for such a manual. You do have to be careful to sort through them for this particular Rieju Marathon. Whether or not the parts link listed above might also have wiring diagrams available would require contact with them. You might have to inquire with a dealer for such if indeed them have such access. Here are links of possible help.
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Https://www.riejuparts.co.uk/
If you perform a search for the rieju marathos pro 125sm and click on IMAGES rather than ALL, you will enounter a number of diagrams of possible interest to you. But you may have to search ebay for such a manual. You do have to be careful to sort through them for this particular Rieju Marathon. Whether or not the parts link listed above might also have wiring diagrams available would require contact with them. You might have to inquire with a dealer for such if indeed them have such access. Here are links of possible help.
https://www.riejumotorcycles.co.uk/m/9/marathon-125-sm-ac
http://www.riejumoto.co.uk/documents.php?type=5
https://www.oemmotorparts.com/oem2.asp?M=rieju
https://www.manualslib.com/manual/958870/Rieju-Marathon-125.html
https://bikez.com/motorcycles/rieju_marathon_pro_125_2011.php
https://en.wikipedia.org/wiki/Rieju