I had this problem which was difficult to diagnose. It turned out to be a Bad Stator assembly. The XT225 has a magneto style ignition. You'll see that as the larger coil in the assembly. Wire is fine like human hair. Varnish can break down, short windings and reduce output. To make matters worse, performance can be temperature dependent and intermittent. I struggled with this for about a year before finding the problem. My bike wouldn't start when hot (sometimes). When Jeannie's stator went south it just quit suddenly. You can take resistance measurements per the service manual to check the windings. This hit both our bikes at approximately 10k miles. Hope this helps. Good luck.