Anyway...I'm a long time biker (45 yrs !) and have rebuilt/restored a number of bikes. All ya'll may know about these but, just in case...
Stat-O-Seals are the best thing since sliced bread. They're a washer with a rubber 'O' ring on the inside diameter. They can be used anywhere you'd use any standard washer. I use them on 2-stroke oil pumps and oil drain plugs, etc....
Go here: http://www.bakerprecision.com/statseal.htm
The link is just one place to get them....do a search.