Just aquired a ox250 a few months ago.
Mine ran a little ruff at idle unit I.
I checked and cleaned my o2 sensor - was very clogged
Replaced the low pressure fuel pumps - only 1 was bad but wanted to start fresh.
Cleaned the vst - was clogged
Not sure which one fixed it but it runs great now. I still need to adjust the throttle position sensor, but need to jerryrig a wire harness first.
If you do a search of the ox66 on this site, you will see these are some pretty common fixes to that engine.
Hope this helps.
