My CB400t from 81 has been acting up lately and seems to be burning oil. i keep needing to put in more oil every 2 weeks, usually 200ml or so. one of the spark plugs is caked with carbon deposits, it isnt wet and oily though, just dry. the other is usually whitish because of an air leak in the carb boot going from the carb to airbox. it runs too lean on that cylinder, i always have to fiddle with the pilot fuel screw. it has 23000 miles, is it possible the rings could be bad? im sure the valves need to be adjusted, but i have no idea how to do that. I have an intermediate level of knowledge with this stuff, is this something I can do myself?