Out of curiousity, did you have to push harder than normal to install the oil filter cover?
You may want to remove the cam and expect to replace the cam bearing...sounds as though it almost seized.
At this point you may want to stay within pushing distance of base (home, trailer, truck)
This video shows a damaged bearing. https://m.youtube.com/watch?v=qcMmleRDxLc
OTOH in the mid seventies, wife and I were climbing the back side of Government Peak near Randsburg, CA after being at Jawbone Canyon with a temp of 113 F. Her 175cc Yamaha enduro had no issues, but my 125cc started to lose power. We stopped for the engine to cool and went on with no problems. The 125cc ran for many miles thereafter.