I did it the factory way, I didn't want to glue them as most people do, brake fluid on new paint would piss me off. Here's the how as best as I can explain, it's not difficult but you want to avoid damaging parts you must reuse, no special tools are needed. Order lenses get a spare just in case they're 89 cents but shipping cost about $8 but they're fast shippers. ID: MG 17.9MM Mineral Glass Watch Crystal 1.0mm thick LINKY http://www.toolsgs.com/cart/browse.asp?subcat=258 1 - Remove Master Cylinder and clean 2- Break out old plastic lens, don't ruin the little metal plate in the window, all plastic must be removed from in the groove to get o-ring out, remove the little round plate, try not to damage o-ring. 3- Place a steel washer that just fits in the window hole (not too thick must fit in groove) slide it to one side in the groove and use a toothpics on the opposite side to hold it over to one side in the groove. 4- The goal is to get the round thin retaining ring out without damage (it's on the outside retaining the sightglass in place) tap on the washer on the edge in the groove from the inside with a hammer & punch, then move the washer to the other side of the groove and tap, it should fly off the bench so don't lose it. 5- Clean the opening, install o-ring, install little round plate, install new 17.9mm Glass. At this point I put a little black silicon around the edge of the glass as a backup seal. 6- Install install the retaining ring, I used a larger steel washer on each side and channel locks to evenly press the retainer back in. Mine just barely stick out after being seated all the way in. Clean excess silicon from glass. 6- I put soap in the sight window and blew air from inside to leak test (no leaks) I can see in now and it looks new for minimun cost!
