lean 1-2 mm?????

 

I'd say keep adjusting 1-2 mm. at a time until the problem stops. If you're trying to get the bike to run cleanly in a 12 it's easy to do but then it may not run right when it's on both wheels. You may have to compromise. I think that if you keep the RPMs up the motor won't bog as much. That would mean lower gearing or adjusting your idle higher. Hope that helps.