You could tap to the next size and put wax on the chutes to trap the aluminum shavings. Clean the chutes out twice and put in new wax each time. Pour in cheap oil, 10w-30 or something, swish it around and drain. Then put in your normal oil. A tiny bit of aluminum shavings shouldnt do anything to your transmission, I had a cotter pin go thru and come out in a million pieces 2 hours of riding later. The transmission doesnt make any funny noises, shifts well and the clutch is all-grip/no-slip.