@notgotaclue You can download the service manual for free from here;
https://www.manualslib.com/manual/1203458/Yamaha-Dt125re-2005.html
And well worth the money is a Haynes manual;
https://www.ebay.co.uk/itm/Haynes-Workshop-Manual-Yamaha-TZR125-DT125R-DT125X-1987-2007-New-Service-Repair/254113315280?hash=item3b2a5579d0:g:Lu4AAOSw5LZcXG04:rk:3🇵🇫1&frcectupt=true
Both have lots of tips and troubleshooting guides!!! 😉